Blind-adaptive decoding of radio signals

ABSTRACT

In a radio receiver, digital baseband signals are processed by a time-domain-to-frequency-domain converter to generate frequency-domain symbols. A blind-adaptive decoder processes the frequency-domain symbols to produce estimates of transmitted data symbols. Frequency-domain equalization may be performed prior to the blind-adaptive decoder performing at least one of blind-adaptive decoding and partially blind adaptive decoding based on information about the transmitted data symbols. The blind-adaptive decoder comprises a combiner that combines the frequency-domain symbols to produce the estimates of the transmitted data symbols.

BACKGROUND OF THE INVENTION I. Field of the Invention

The present invention relates to networks of wireless transceivers thatimplement Carrier Interferometry (CI) and/or CI-based coding.

II. Description of the Related Art

A wideband signal, such as a direct-sequence CDMA (DS-CDMA) signal,transmitted in a multipath environment experiences a frequency-selectivefade. If the duration of the data bits is smaller than the multipathdelay, the received signal experiences inter-symbol interferenceresulting from delayed replicas of earlier bits arriving at thereceiver.

Improved DS-CDMA systems use interference cancellation to increasecapacity; however, the required signal-processing effort is proportionalto at least the cube of the bandwidth. Furthermore, DS-CDMA issusceptible to near-far interference, and its long pseudo-noise (PN)codes require long acquisition times. For these reasons, OrthogonalFrequency Division Multiplexing (OFDM) has been merged with DS-CDMA.

In multicarrier CDMA (MC-CDMA), a spreading sequence is converted fromserial to parallel. Each chip in the sequence modulates a differentcarrier frequency. Thus, the resulting signal has a PN-coded structurein the frequency domain, and the processing gain is equal to the numberof carriers.

In multi-tone CDMA, or multicarrier DS-CDMA, the available spectrum isdivided into a number of equal-width frequency bands used to transmit anarrowband direct-sequence waveform. In U.S. Pat. No. 5,504,775, binaryCDMA code symbols are applied to individual carriers in an OFDM system.U.S. Pat. Nos. 5,521,937, 5,960,032, and 6,097,712 describe multicarrierDSSS systems having direct-sequence coding on each subcarrier.

U.S. Pat. No. 5,955,992, PCT Pat. Appl. No. PCT/US99/02838, and U.S.Pat. Pub. No. 2002034191 describe CI, which is a multicarrier protocolimplemented with polyphase codes. These polyphase codes may be used formultiple access, spread spectrum, channel coding, or encryption, asdescribed in U.S. Provisional Appl. 60/259,433, filed Dec. 31, 2000.Multiple carriers are redundantly modulated with data streams that areorthogonalized by virtue of different sets of phases encoding each datastream. Interferometry of the carriers provides the means toorthogonalize the data streams, whether the carriers are combined orprocessed separately. Weights applied to the carriers shape the carriersuperpositions, thus, allowing CI signals to appear as single-carrierwaveforms, such as Time Division Multiple Access (TDMA) or DS-CDMAsignals.

Adaptive antenna arrays may be implemented with DS-CDMA communicationsto provide significant improvements in range extension, interferencereduction, and system capacity. To identify a particular user, a DS-CDMAsystem demodulates Walsh codes after converting the received signal fromanalog radio frequency (RF) to digital. Therefore, an adaptive antennaarray requires information about the user codes, or it needs todemodulate many different incoming RF signals to track mobile users.These methods are complex processes that are more difficult to implementthan tracking users in non-CDMA systems. Furthermore, the widebandnature of DS-CDMA signals restricts the effectiveness of beam forming,interference nulling, spatial interferometry multiplexing, and othertechniques employed by adaptive antenna arrays.

U.S. entitled “CI Multiple Input, Multiple Output,” filed on Nov. 22,2000, describes applications of multiple-input, multiple-outputprocessing (such as antenna-array processing) to CI signals. CIprocessing allows wideband single-carrier signals, such as DS-CDMAtransmissions, to be processed as a plurality of narrowband components.This simplifies array processing by facilitating beam forming, nullsteering, space-frequency processing, as well as other adaptive arrayprocessing techniques. U.S. Pat. No. 4,901,307 introduces the concept ofmarginal isolation, which is another method of exploiting spatialdivision multiplexing in communication networks. Since cellularimplementations of DS-CDMA are typically interference limited, evensmall reductions in the overall power level of the system allow forincreased system capacity.

Ad-hoc networks allow subscriber units to perform base stationfunctions. This allows micro-cell subnetworks, which lowers overallsystem power levels and improves spectral efficiency. U.S. Pat. No.5,943,322 describes an adaptable DS-CDMA network that uses acontrol-signal channel to assign base-station functions (e.g., powercontrol and synchronization) to a subscriber unit. U.S. Pat. No.6,233,248 provides for multi-address transmissions to be sent on commonpaths between nodes until the paths diverge. U.S. Pat. No. 5,422,952allows signals for a particular user to be transmitted throughout theentire network. Different transmissions are provided with unique PNcodes.

None of the prior-art references describe the use of CI, CI-basedprotocols, or CI coding in ad-hoc networks. Thus, none of the prior-artreferences can provide the improved bandwidth efficiency, enhanced powerefficiency, increased range, increased throughput, and superior immunityto multipath, jamming, and co-channel interference enabled by thecombination of CI and adaptable networks.

SUMMARY OF THE INVENTION

Applications of CI to ad-hoc networking provide substantial performanceimprovements that can be used for any combination of range extension,transmission-power reduction, increased throughput, and improvedbit-error rates. Performance improvements resulting fromfrequency-domain processing are particularly useful in ad-hoc networks(as well as in micro-cell networks and networks that employ relays)where interference and multipath typically impede performance. CI pulseshaping also increases throughput (typically characterized as a doublingof throughput), which can be used to increase the number of users,generate higher data rates, and/or provide channel coding.

Adaptations of CI to conventional multicarrier protocols (such as OFDMand MC-CDMA) eliminate the high peak-to-average-power ratios (PAPR)associated with conventional multicarrier protocols. Low PAPR allowslow-dynamic-range amplifiers to be used, resulting in substantial costand power savings.

Conventional codes, such as multiple-access codes, channel codes,spreading codes, etc., may be implemented with CI chip shapes.Alternatively, polyphase codes based on mathematical relationshipsbetween CI sub-carriers may be provided.

Applications of CI coding are extended to identifying and addressingnetwork transmissions. CI transceivers are adapted to performnetwork-control functions. CI coding facilitates routing in ad-hoc andpeer-to-peer networks. Networks are adapted to perform array processingwith signals received from, and transmitted by, groups of subscriberunits. Other applications and embodiments of the invention are apparentfrom the description of preferred embodiments and the claims thatfollow.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A illustrates a plurality of CI carriers having phase fronts thatare aligned at a specific time. The CI carriers combine to generate aplurality of superposition signals that are orthogonal to each other intime.

FIG. 1B illustrates an in-phase superposition of CI carriers of acarrier set that produces a superposition signal corresponding to a sumof the superposition signals shown in FIG. 1A

FIG. 1C illustrates two sets of orthogonal superposition signals. Thesignals in each set are orthogonal to each other. The signals in a firstset are substantially orthogonal to signals in a second set.

FIG. 1D shows a summation of two orthogonal sets of CI signals whereinsignals in a first set are quasi-orthogonal to signals in a second set.

FIG. 2A illustrates phase relationships between two orthogonalsinusoidal waveforms that demonstrate a mathematical basis of CIprocessing.

FIG. 2B illustrates relationships between two orthogonal sinusoidalwaveforms.

FIG. 3A illustrates a phase offset of adjacent samples shown in FIG. 2A.

FIG. 3B illustrates a phase offset of adjacent samples shown in FIG. 2B.

FIG. 4A shows samples distributed uniformly around a unit circle in thecomplex plane.

FIG. 4B shows samples distributed uniformly around a unit circle in thecomplex plane.

FIG. 4C is a normalized complex-plane representation of samples of asignal having a particular frequency collected at a sampling rate thatequals, or is some sub-harmonic frequency of, the signal frequency. Eachsample corresponds to an integer number of full rotations in the complexplane.

FIG. 5A shows a set of 16 octonary CI code vectors of length 8.

FIG. 5B shows correlations of the 16 octonary codes shown in FIG. 5A.

FIG. 6A illustrates basic components of a CI-code generator.

FIG. 6B illustrates basic components of a CI transmitter.

FIG. 6C illustrates basic components of a CI decoder.

FIG. 7 illustrates the relationship between basic CI symbol values w_(n)and data symbols s_(n) processed with CI code chips to produce the CIsymbol values w_(n).

FIG. 8A illustrates basic components of a CI coding system and a CIdecoding system.

FIG. 8B shows a system diagram of a CI transceiver.

FIG. 9A illustrates a tree network that may be implemented in someaspects of the present invention.

FIG. 9B illustrates a network design that permits a plurality ofcommunication paths to each node.

FIG. 9C illustrates a network design adapted to provide array processingperformance advantages.

FIG. 9D illustrates a concentric ring network configuration.

FIG. 9E illustrates a network configuration adapted to the geographicdistribution of a plurality of subscribers located along a roadway.

FIG. 9F illustrates a plurality of nodes adapted to route CIcode-addressed signals.

FIG. 9G illustrates a simple tree-style CI-based network of the presentinvention.

FIG. 9H illustrates a simple CI-based network wherein each node can bereached by a plurality of paths.

FIG. 9I illustrates a network characterized by two communication pathsto a common destination node.

FIG. 9J illustrates a network having a plurality of crossingcommunication paths.

FIG. 10A illustrates a multi-level cellular architecture that may beemployed by systems and methods of the present invention.

FIG. 10B illustrates three adjacent cells in a cellular network of thepresent invention.

FIG. 10C shows a cellular architecture of the present invention thatincludes a plurality of cells and a plurality of base stations locatedon cell boundaries.

FIG. 10D illustrates a cellular network of the invention including aplurality of cells, a plurality of base stations, and a plurality ofsubscriber units.

FIG. 11A illustrates a CI transceiver adapted to perform routing.

FIG. 11B illustrates an alternative embodiment of a CI transceiveradapted to perform routing.

FIG. 11C illustrates an alternative embodiment of a CI transceiveradapted to perform routing.

FIG. 11D illustrates a method in which a transceiver in a network isprovided with control information that includes information used togenerate one or more array-processing weights.

FIG. 11E illustrates a method in which an individual network transceiveris adapted to perform array processing relative to local conditions. Thetransceiver can be adapted to optimize transmit/receive operationsrelative to signal quality measured at the transceiver.

FIG. 11F illustrates an array-processing method that employs at leastone central processor to provide beam-forming operations across aplurality of spatially distributed network transceivers. The centralprocessor may direct the network transceivers to apply weights totransmitted and/or received signals. Alternatively, the centralprocessor may perform array processing by providing weights to signalsit transmits to, and receives from, network transceivers. The centralprocessor may be adapted to perform various combining operations,including CI combining.

FIG. 12A illustrates a method for providing CI-coded transmissions ofinformation and control signals.

FIG. 12B illustrates a method for managing network control in a CInetwork by one or more subscriber units adapted to function as basestations.

FIG. 12C illustrates a network-control method of the present invention.

FIG. 12D shows a routing method of the present invention.

FIG. 13A shows a relay method of the present invention.

FIG. 13B illustrates an alternative embodiment of a relay method of theinvention.

FIG. 13C illustrates a transceiver processing and routing method of theinvention.

FIG. 13D illustrates an alternative transceiver processing and routingmethod of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The description of the preferred embodiments assumes that the reader hasa familiarity with CI described in the following publications, which areincorporated by reference:

-   -   1. B. Natarajan, C. R. Nassar, S. Shattil, M. Michelini,        “Application of interferometry to MC-CDMA”, accepted for        publication in IEEE Transactions on Vehicular Technology.    -   2. C. R Nassar, B. Natarajan, and S. Shattil, “Introduction of        carrier interference to spread spectrum multiple access,” IEEE        Emerging Technologies Symposium, Dallas, Tex., 12-13 Apr. 1999.    -   3. B. Natarajan and C. R. Nassar, “Introducing novel FDD and FDM        in MC-CDMA to enhance performance,” IEEE Radio and Wireless        Conference, Denver, Colo., Sep. 10-13, 2000, pp. 29-32.    -   4. Z. Wu, C. R. Nassar, A. Alagar, and S. Shattil, “Wireless        communication system architecture and physical layer design for        airport surface management,” 2000 MEE Vehicular Technology        Conference, Boston, Mass., Sep. 24-28, 2000, pp. 1950-1955.    -   5. S. Shattil, A. Alagar, Z. Wu and C. R. Nassar, “Wireless        communication system design for airport surface management—Part        I: Airport ramp measurements at 5.8 GHz,” 2000 IEEE        International Conference on Communications, Jun. 18-22, 2000,        New Orleans, pp. 1552-1556.    -   6. B. Natarajan, C. R. Nassar, and S. Shattil, “Carrier        Interferometry TDMA for future generation wireless—Part I:        Performance,” accepted for publication in IEEE Communications        Letters.    -   7. Z. Wu, C. R. Nassar, and S. Shattil, “Capacity enhanced        DS-CDMA via carrier interferometry chip shaping,” IEEE 3G        Wireless Symposium, May 30-Jun. 2, 2001, San Francisco, Calif.    -   8. Z. Wu, C. R. Nassar, and S. Shattil, “Frequency diversity        performance enhancement in DS-CDMA via carrier interference        pulse shaping,” The 13^(th) Annual International Conference on        Wireless Communications, Calgary, Alberta, Canada, Jul. 7-10,        2001.    -   9. C. R. Nassar and Z. Wu, “High performance broadband DS-CDMA        via carrier interferometry chip shaping,” 2000 International        Symposium on Advanced Radio Technologies, Boulder, Colo., Sept.        6-8, 2000, proceeding available online at        http://ntai.its.bldrdoc.gov/meetings/art/index.html.    -   10. Z. Wu and C. R. Nassar, “MMSE frequency combining for        Cl/DS-CDMA,” IEEE Radio and Wireless Conference, Denver, Colo.,        Sep. 10-13, 2000, pp. 103-106.    -   11. D. Wiegand, C. R. Nassar, and S. Shattil, “High Performance        OFDM for next generation wireless via the application of carrier        interferometry,” IEEE 3G Wireless Symposium, May 30-Jun. 2,        2001, San Francisco, Calif.    -   12. B. Natarajan, C. R. Nassar, and S. Shattil, “Exploiting        frequency diversity in TDMA through carrier interferometry,”        Wireless 2000: The 12^(th) Annual International Conference on        Wireless Communications, Calgary, Alberta, Canada, Jul. 10-12,        2000, pp. 469-476.    -   13. B. Natarajan, C. R. Nassar, and S. Shattil, “Throughput        enhancement in TDMA through carrier interferometry pulse        shaping,” 2000 IEEE Vehicular Technology Conference, Boston,        Mass., Sep. 24-28, 2000, pp. 1799-1803.    -   14. S. A. Zekevat, C. R. Nassar, and S. Shattil, “Smart antenna        spatial sweeping for combined directionality and transmit        diversity,” accepted for publication in Journal of Communication        Networks: Special Issue on Adaptive Antennas for Wireless        Communications.    -   15. S. A. Zekevat, C. R. Nassar, and S. Shattil, “Combined        directionality and transmit diversity via smart antenna spatial        sweeping,” 38 ^(th) Annual Allerton Conference on        Communications, Control, and Computing, Champaign-Urbana, Ill.,        Oct. 4-6, 2000.    -   16. S. Shattil and C. R. Nassar, “Array Control Systems For        Multicarrier Protocols Using a Frequency-Shifted Feedback        Cavity” IEEE Radio and Wireless Conference, Denver, Colo., Aug.        1-4, 1999.    -   17. C. R. Nassar, et. al., MultiCarrier Technologies for Next        Generation Multiple Access, Kluwer Academic Publishers: 2001.

Applications of CI, array processing, spatial interferometry, andrelated systems and methods are cited in the following patents andpatent applications, which are hereby incorporated by reference:

1. U.S. Pat. No. 5,955,992

2. U.S. Pat. No. 6,008,760

3. U.S. Pat. No. 6,211,671

4. U.S. Pat. No. 6,331,837

5. U.S. Pat. No. 6,348,791

6. PCT Appl. No. PCT/US99/02838

7. PCT Appl. No. PCT/US00/18113

8. U.S. patent application Ser. No. 09/347,182

9. U.S. patent application Ser. No. 09/472,300

10. U.S. patent application Ser. No. 09/433,196

11. U.S. patent application Ser. No. 09/393,431

12. U.S. patent application Ser. No. 09/718,851

13. U.S. patent application Ser. No. 09/703,202

14. U.S. patent application Ser. No. 10/034,386

15. U.S. patent application Ser. No. 10/078,774

16. U.S. patent application Ser. No. 10/131,163

17. U.S. Provisional Pat. Appl. No. 60/163,141

18. U.S. Provisional Pat. Appl. No. 60/219,482

19. U.S. provisional Pat. Appl. No. 60/259,433

20. U.S. provisional Pat. Appl. No. 60/286,850

1. Definitions

Various terms used in the descriptions of CI methods and systems aregenerally described in this section. The descriptions in this sectionare provided for illustrative purposes only, and are not limiting. Themeaning of these terms will be apparent to persons skilled in therelevant art(s) based on the entirety of the teachings provided herein.These terms may be discussed throughout the specification and the citedreferences with additional detail.

An address, or network address, as used herein, describes any set ofsymbols used to identify a particular network node or transceiver. Anaddress may include symbols in a header or other part of a datatransmission. An address may correspond to a code used to encode atransmission. In some applications of the invention, an address mayspecify one or more routes through a network. For example, multipleaddresses may indicate one or more preferred paths through the network.Alternatively, a message address may be constructed via somemathematical relationship of node addresses that indicate one or morepaths to at least one destination node. In some aspects of theinvention, the message address may be changed as the message propagatesthrough the network.

The term carrier signal, or carrier, when used herein, refers to atleast one electromagnetic wave having at least one characteristic thatmay be varied by modulation. Subcarriers may be referred to as carriers.Other wave phenomena, such as acoustic waves, may be used as carriers.Carrier signals may include any type of periodic signal. Carrier signalsmay include sinusoids, square waves, triangle waves, wavelets, and/orarbitrary waveforms. A carrier signal is capable of carrying informationvia modulation. A carrier signal may be modulated or unmodulated.Multicarrier signals may include multi-frequency signals, multi-spatialsignals, multi-directional signals, multi-polarization signals, multiplecoded signals, multiple sub-space signals, multi-phase-space signals,time-domain (discreet-time) signals, and/or any other set ofelectromagnetic signals having different orthogonal or quasi-orthogonalvalues of at least one diversity parameter. A code sequence can beregarded as a carrier signal. A subcarrier may include more than onesignal and more than one type of signal.

Channel compensation describes signal processing performed on at leastone transmitted and/or received signal according to measured and/orcalculated channel fluctuations. Channel compensation may include any ofvarious blind adaptive techniques. Alternatively, channel compensationmay employ at least one pilot or training signal to probe the channel.Known signals can be used to compensate for various multipath effects(such as fading and/or inter-symbol interference), mitigate multi-userinterference, and/or remove jamming signals. Channel compensation mayemploy a combination of adaptive and reference-signal processing.Channel compensation may include adaptive channel equalization. Channelcompensation in a CI and/or antenna-array system may employ some type ofcombining.

Channel estimation describes any combination of blind adaptivetechniques and reference-signal processing to determine signaldistortion resulting from the effects of at least one communicationchannel. In one example, a pilot symbol is transmitted periodically froma remote transmitter. A local receiver exploits the known transmissiontime, frequency, polarization, and/or any other diversity-parametervalue of at least one pilot symbol to process the transmitted pilotsymbol and estimate the distortion caused by the channel environment. Onthe basis of an estimated value, distortion in the received data symbolsis compensated. In some aspects of the invention, a pilot tone may beemployed.

CI codes, as used herein, may include basic CI codes or advanced CIcodes. CI codes are based on mathematical relationships between CIcarriers and phase spaces. CI codes can be used as direct-sequencecodes, multicarrier codes (e.g., MC-CDMA), etc. Applications of CI codescan be extended to any application of conventional binary directsequences, including but not limited to, spread spectrum, multipleaccess, channel coding, encryption, anti-jamming, etc. CI codes may beapplied across any set of orthogonal or quasi-orthogonaldiversity-parameter values or subspaces. Although CI codes can berepresented with respect to phase relationships generated by vectorprecession in the complex plane, the implementation of CI coding can beextended to circular, elliptical, and linear polarizations.

A coder, as used herein, describes any system, device, or algorithmadapted to generate spread-spectrum codes, multiple-access codes,channel codes, encryption codes, multi-level codes, compression codes,hybrid codes, and CI codes. A coder may interleave coded data symbols inone or more diversity-parameter spaces. The coder may provide channelcoding to the data symbols. A CI coder, includes any algorithm, device,or system adapted to combine, merge, or otherwise impress at least onedata symbol onto a plurality of CI code chips or carriers. The CIencoder may impress each CI code chip onto one or morediversity-parameter values prior to, or after, impressing data symbolsonto the CI code. A CI code may be impressed onto at least oneintermediate-frequency (IF) carrier. The CI encoder may performmultiplexing. For example, the CI encoder may encode data streams ontodifferent CI codes. The CI encoder may employ other diversity parameterson which to multiplex multiple data streams.

A combiner, as used herein, describes any system, device, and/oralgorithm adapted to combine a plurality of signals, samples, or symbolvalues. A combiner may combine multiple carriers or signal values togenerate a superposition signal. A combiner may provide weights tocarriers or signal values to generate one or more superposition signalshaving predetermined characteristics, such as time domain, frequencydomain, spatial domain, sub-space domain, and/or other physicalcharacteristics. A combiner may compensate for noise, interference,and/or distortion.

Combining often involves generating weights based on channel estimates.The weights may be adapted relative to some performance measurement,such as probability of error, bit-error rate (BER), signal-to-noiseratio (SNR), signal-to-noise-plus-interference ratio (SNIR), and/or anyother signal-quality parameter. Possible combining techniques includeequal-gain combining (EGC), orthogonal restoring combining (ORC), andminimum mean squared error combining (MMSEC). Performance measurementsmay include any combination of instantaneous and averaged performancemeasurements. Averaging may be performed over one or more diversityparameters.

A combiner may perform combining in more than one diversity-parameterspace. For example, MMSE combining may be performed in the frequencydomain to generate a plurality of combined signals that may be processedvia EGC in the time domain. Other types of combining, as well ascombining in different dimensions, may be performed. Combining may alsobe performed as a receive-side array-processing technique. Arrayprocessing (e.g., spatial combining) may be integrated into othercombining operations, such as CI subcarrier combining.

A communication channel, as described herein, typically comprises an RFchannel. A communication channel may include any propagation mediumand/or path between at least one transmitter and at least one receiver.A communication channel may be natural and/or man-made, including, butnot limited to, air, space, wire, cable, waveguide, microstrip,strip-line, optical fiber, and liquid.

A control channel is a communication channel in which controlinformation is transmitted.

Control information, as used herein, includes any information used toset, monitor, identify, adapt, or change communications and/ortransceiver operations in a network. Control information may be providedfor power control, synchronization, routing, channel assignments, codeassignments, addressing, identification, acknowledgment, transfer ofnetwork control, etc. Control information may include pilot signals,training symbols, addresses, tags, codes, parity symbols, reference(e.g., timing, phase, power, frequency) signals, and/ortransceiver-control signals.

A decoder, as used herein, describes any system, device, or algorithmcapable of decoding an encoded information (e.g., data) signal. Adecoder typically decodes an encoded signal with respect to one or morereference signals (e.g., codes, decode sequences, code keys, etc.).Decoding may take the form of a correlation process, matched filtering,or any kind of processing (e.g., complementary processing) that extractsat least one desired information signal from the coded signal. In apreferred embodiment, collected samples are phase shifted with respectto at least one code prior to being summed. In some multicarriersystems, it is impractical to perform matched filtering or correlation.Rather, data symbols are obtained from the output bins of a Fouriertransform process. Similarly, other types of transforms or inversetransforms may be performed in a decoder.

A destination node, as used herein, describes a network transceiverselected to receive at least one communication signal. A destinationnode may describe a local destination node within a particular network.Alternatively, a destination node may describe the final destination(s)of at least one particular transmission.

The term diversity-parameter, as used herein, describes at least onesignal characteristic that enables a signal to be distinguished fromanother signal. Examples of diversity parameters include, but are notlimited to, amplitude, spatial gain distribution, directionality,energy, power, linear polarization direction, circular/ellipticalpolarization direction, circular/elliptical polarization rotation rate,mode, frequency, time, code, phase, coherence length, and phase space.Diversity parameters may include proportions of two or morediversity-parameter values. Diversity parameters may include anycombination of unique signal characteristics. Diversity parameters mayinclude diversity-parameter subspaces, such as spatial sub-spaces. Acommon diversity parameter, as used herein, is a range of at least onediversity-parameter value into which electromagnetic signals may bemapped.

Duplexing, as used herein, describes any processing technique adapted toseparate transmitted and received signals. Various multiple-accesstechniques may be adapted to perform duplexing. Time-division duplexing(TDD) may be provided with respect to orthogonal time-domain slots. InCI-based protocols, TDD may be provided with respect to time-domaincharacteristics of multicarrier superposition signals and/or time-offsetcoding applied to CI. Frequency-division duplexing (FDD) provides forseparation of signals characterized by different frequency bands. Themulticarrier structure of CI enables FDD. Even spread-spectrumprotocols, such as DS-CDMA, may benefit from CI-enabled FDD without thereduced frequency-diversity benefits inherent in conventional FDD. Codedivision duplexing (CDD) may be provided.

CI phase-division duplexing (CI-PDD) describes the separation ofmulticarrier signals having different phase spaces. Transmitted andreceived CI signals may be separated due to the orthogonality (orquasi-orthogonality) of the phase spaces. One application of CI-PDDinvolves applying a matched filter to desired received components toremove the effects of transmitted signals (as well as undesired receivedsignals). Cancellation may be used to electromagnetically isolatereceivers from transmitters that use the same time and frequency bandsfor transmission. Some of these cancellation techniques are described inU.S. Pat. No. 6,348,791, which is incorporated by reference.Polarization division duplexing includes orthogonal polarizationduplexing (OPDD) and quasi-orthogonal polarization duplexing (QPDD).OPDD is a well-known method of using orthogonal polarizations to doublechannel capacity. For example, linear polarized antennas may be orientedperpendicular to each other to provide isolation. OPDD involves usingknown ratios of co-channel interference to cancel the interferingsignals. Circular polarization duplexing (CPD) may employ oppositepolarization spins. CPD may employ orthogonal polarization frequencies.OPDD, QPDD, and CPD may employ three-dimensional (i.e., x-y-z axis)polarizations

Coherence time division duplexing (CTDD) may be used to removeinterfering signals having different time offsets. In CTDD, aninformation signal modulated onto a wideband signal is transmitted alongwith a decode signal. A predetermined time offset between the modulatedand decode signals allows a receiver to extract the information signalwithout any knowledge of the wideband signal. In CI-based signals, atime offset corresponds to a vector of phase offsets corresponding tothe CI sub-carriers. Wideband signals, such as additive white Gaussiannoise, chaotic signals, pseudo-random signals, etc., may be provided (orclosely approximated) by a predetermined weighted set of CIsub-carriers. Orthogonal CTDD pertains to time-offset differencesbetween transmitted and received signals that exceed the inverse of thecoherence bandwidth of the signals. Quasi-orthogonal CTDD occurs whenthe time-offset differences between desired receive signals andinterfering transmissions do not exceed the inverse coherence bandwidthof the signals. This causes overlap interference in the matched-filteroutput. The overlap interference may be removed via cancellation.

An information signal, as used herein, describes one or more signalsthat convey some form of useful information via magnitude, phase,frequency, polarization, mode, direction, and/or some signal propertyderived therefrom. CI-based information signals may include any type ofcommunication signal, such as, but not limited to, voice, data, andtext. Information signals may include any of various types ofremote-sensing signals, such as radar signals, Lidar signals,spectroscopy signals of various types (e.g., absorption, scatter,luminescence, resonant, emission, harmonic, intermodulation, etc.),probing signals, and imaging signals (e.g., X-ray, gamma-ray,ultrasound, seismic survey, acoustic, sonar, optical, pulse radio,spread spectrum, etc.). Any information signal may be considered to be aCI-based signal if it is processed via CI signal-processing techniques.Thus, a received non-CI signal may be converted into a CI signal bydecomposing the received signal into orthogonal sub-carrier components.

The term modulation, as used herein, refers to any method of impressinga signal (such as an information signal, a code signal, and/or asub-carrier) onto an electromagnetic signal. Modulation describes theadjustment of one or more physical signal characteristics with respectto an information signal. Modulation may be combined with spreading.Signals, such as analog and/or digital information signals, may beimpressed onto one or more carrier signals via any combination ofmodulation techniques, including, but not limited to, amplitudemodulation, phase modulation, frequency modulation, pulse modulation,and/or polarization modulation. Pulse modulation (such as CI-pulsemodulation) may include Pulse-Amplitude Modulation (PAM), pulse-codemodulation, pulse-frequency modulation, pulse-position modulation,and/or pulse-width modulation.

CI signal generation sometimes includes modulation, PAM, Frequency ShiftKeying (FSK), Phase Shift Keying (PSK), and Quadrature AmplitudeModulation (QAM). Coded modulation, such as trellis-code modulation, maybe performed. Data symbols may be modulated onto a code sequence, suchas a multiple-access code, a spreading code, an encryption code, achannel code, etc. A code sequence may include digital and/or analogsignals. Examples of code sequences include direct-sequence codes,MC-CDMA codes, CI codes, Cl/DS-CDMA codes, frequency-hopping codes,chirp codes, coherence-multiplexing codes, sub-channel codes, and codelength division multiplexing codes. Some types of modulation can includethe formation of code-chip values, continuous-code values, and/orcode-chip sequences based on data-symbol values. Data symbols may beinput to a code-generation process.

A network control station (also referred to as a base station) is anynetwork transceiver adapted to perform network control operations, suchas communication control, power control, synchronization, assignment ofoperating parameters to other network transceivers, spectrum management,load balancing, network configuration, code assignment, channelselection, performance monitoring, performance optimization, routing,authentication, verification, channel estimation, etc.

A network transceiver is any transceiver adapted to operate in anetwork. A network transceiver may include a base station, access point,relay, router, and/or subscriber unit.

A receiver, as used herein, includes any system, device, or process thatemploys any combination of detection and estimation. Detection is thetask of determining if a predetermined signal is present in anobservation. Estimation is the task of obtaining or determining valuesof one or more signal parameters. A receiver may perform varioussignal-processing operations, including, but not limited to, filtering,channel selection, A/D conversion, AGC, timing recovery, carrieracquisition, carrier recovery, bandwidth adjustment, sample-rateadjustment, matched filtering, soft-decision quantization, arrayprocessing, error detection, error correction, amplification, decoding,DC-signal removal, equalization, combining, spectral shaping,noise-bandwidth control, spectral translation, amplifier linearization,de-interleaving, in-phase/quadrature-phase gain and phase balancing,etc.

An RF front end describes any device or system adapted to convertbaseband or IF signals to RF for transmission. An RF front end may beadapted to receive and convert RF signals to baseband or IF. An RF frontend may be adapted to perform RF, IF, and/or baseband signal processingto prepare a received RF signal for IF or baseband processing.Similarly, RF, IF, and/or baseband processing may be provided to preparea baseband or IF signal for coupling into an RF communication channel.An RF front end may perform array processing.

A source node is a transceiver in a network from which a transmissionoriginates. A source node may be defined relative to a given network.For example, although a base station may receive a transmission andretransmit the information into a given network, the base station may beregarded as the source node relative to the given network.Alternatively, the source of the information may be identified as thesource node.

A subscriber, or subscriber unit, as used herein, is a transceiver thatis capable of acting as an information source and/or an information sinkin a network. A subscriber is typically provided with communicationservices from at least one network. A subscriber typically communicatescommunication information with other subscribers. However, thiscommunication information may be routed through other subscribers ornon-subscriber devices. Thus, a subscriber is typically provided with atleast one communication link to at least one other transceiver, such asa base station, access point, relay, router, and/or another subscriber.

A subspace, as used herein, describes a signal space that can include aplurality of signals having at least one common diversity parametervalue (or range of values) and, preferably, is characterized by somemeans to separate at least one of the signals from at least one other ofthe signals. For example, each of a plurality of signals sharing thesame frequency band, but transmitted by a different transmitter elementcharacterized by some unique physical property (i.e.,diversity-parameter value), may be characterized as a sub-space signal.Preferably, a plurality of receiving antennas are adapted to produce aplurality of algebraically unique combinations of the transmittedsignals. Accordingly, algorithms and/or processors are provided toseparate at least one desired signal from at least one interferingsignal.

A transmitter, as used herein, includes any system, device, or processadapted to couple one or more signals into at least one communicationchannel. A transmitter may perform one or more signal-processingoperations to prepare the signal for propagation in a channel. Forexample, transmitter-side signal processing may include D/A conversion,frequency up-conversion, filtering, spreading, predistortion, and/orarray processing.

A CI transmitter may be implemented via any of many differenttechniques. The present invention anticipates design variations ofCI-based transmitters. A CI/DS-CDMA transmitter, as well as any other CItransmitter, is characterized by the signals generated. In particular, aCI/DS-CDMA transmitter is any device, system, or algorithm capable ofimpressing information onto a plurality of carriers and adjusting (e.g.,weighting) the carriers to provide a superposition signal havingpredetermined time-domain characteristics. Such time-domaincharacteristics may include a signal resembling a direct-sequence code.

An unlicensed frequency band refers to any frequency band that isallocated for unlicensed use by the Federal Communications Commission oran equivalent national or international regulatory organization. Forexample, unlicensed frequency bands for wireless LAN are specified inthe IEEE 802.11 standards.

2. Introduction to Carrier Interferometry

Various aspects of the present invention are based on CI. Other aspectsof the invention are particularly applicable to CI methods and systems.There are too many variations, permutations, and specificimplementations of CI to describe in this introduction. Accordingly, thedescriptions and examples of CI described herein are not intended tolimit the scope of how CI is defined, but rather to illustrate a few ofthe many ways that the present invention may be implemented.Descriptions of CI are also intended to clarify some of the aspects andembodiments of the present invention.

Inter-symbol interference occurs when a reflected signal travels adistance sufficiently greater than the distance traversed by aline-of-sight signal so as to cause a delay greater than the duration ofa data symbol. CI avoids inter-symbol interference by transmitting datasymbols on narrowband carriers. Multipath fading occurs when anarrowband signal traverses two paths having a half-cycle phasedifference. CI avoids the problem of multipath fading by transmittingeach data symbol on multiple carriers that are adequately separated withrespect to frequency or some other diversity parameter. Redundantmodulation typically reduces bandwidth efficiency. CI avoids the problemof reduced bandwidth efficiency by modulating up to 2N data symbols oneach of N carriers. Increased interference on one or more carrierstypically increases probability of error. CI avoids the problem ofincreased interference and probability of error by exploitinginterferometry to orthogonalize data symbols modulated on the samecarriers. Thus, CI achieves higher throughput with better signal qualitythan any other multiple-access protocol.

FIG. 1A illustrates a basic form of CI in which a plurality of CIcarrier sets 105A, 105B, and 105C each have phase fronts aligned at aspecific time t₁, t₂, and t₃, respectively. A plurality of superpositionsignals 110A, 110B, and 110C result from a summation of each carrier set105A, 105B, and 105C, respectively. The superposition signal 110Aillustrates a pulse envelope centered at time t₁. All of the carriers105A are in-phase at time t₁ and thus, combine constructively. Thesuperposition signal 110A has a maximum magnitude at time t₁. At othertimes (e.g., times t₂ and t₃), the carriers in carrier set 105A combinedestructively, resulting in low or undetectable signal levels.

In CI, the individual signal components 105A, 105B, and 105Ccontributing to a CI pulse 110A, 110B, and 110C, respectively, orinformation symbol s_(n) have an extended duration T_(s) relative to thepulse width T_(pulse). The extended symbol duration T_(s) (i.e., theduration of component waveforms corresponding to a symbol s_(n)) reducesspectral sidelobes associated with the transmitted information symbols_(n). The extended waveform shape can be overlapped with extendedwaveforms associated with other symbols s_(n′) (n′≠n). Naturally,interference will occur between the waveforms associated with differentdata symbols. However, CI coding can be employed to provideorthogonality (or quasi-orthogonality) between the composite waveforms(i.e., the data symbols s_(n)).

Although multicarrier-based CI signals (such as signals 110A, 110B, and110C) can resemble sinc-shaped pulses, which are orthogonalized bytime-domain pulse positioning, it is important to note thatmulticarrier-based CI signals are composed of multicarrier (e.g.,multi-frequency) components and are typically processed (e.g., generatedand/or decomposed) in the frequency domain.

The signal 110A results from an addition of N carriers that have auniform frequency separation f_(s). FIG. 1A illustrates a simple case ofrectangular (i.e., non-tapered) windowing of the carrier amplitudes. TheCI carriers are uniformly spaced in frequency f_(n)=f_(o)+nf_(s), wheref_(o) is some zero or non-zero offset frequency, f_(s) is a non-zeroshift frequency, and n is some integer or set of integers. Asuperposition CI signal, such as signal 110A, is expressed by:

${{e(t)} = {\sum\limits_{n = 1}^{N}e^{t{\lbrack{{{({\omega_{c} + {n\; \omega_{s}}})}t} + {n\; {\Delta\varphi}}}\rbrack}}}},$

and has a magnitude of:

${{e(t)}} = {{\frac{\sin \left( {{N\left( {{\omega_{s}t} + {\Delta\varphi}} \right)}/2} \right)}{\sin \left( {\left( {{\omega_{s}t} + {\Delta\varphi}} \right)/2} \right)}}.}$

The CI signals are periodic with period 1/f_(s) for an odd number ofcarriers N and with period 2/f_(s) for an even number of carriers N. Themain lobe has a duration 2/Nf_(s) and each of the N-2 side lobes has aduration 1/Nf_(s). The amplitude A(l) of the l^(th) side lobe withrespect to the main lobe amplitude is:

${A(l)} = \frac{1}{N\; {\sin \left( {{\pi \left( {l + {1/2}} \right)}/N} \right)}}$

Applying a phase shift of nΔϕ_(k) to each n^(th) carrier shifts the CIenvelope in time by Δt=Δϕ_(k)/2πf_(s). Therefore, N signals can bepositioned orthogonally in time. The phase shifts can provide necessaryphase relationships to create the desired timing of the informationsignal received by at least one receiver (not shown).

The cross correlation between users is:

${{R_{cc}(\tau)} = {\frac{1}{2f_{s}}\frac{\sin \left( {N\; 2\pi \; f_{s}{\tau/2}} \right)}{\sin \left( {2\pi \; f_{s}{\tau/2}} \right)}{\cos \left( {\left( {N - 1} \right)2\pi \; f_{s}{\tau/2}} \right)}}},$

where τ is the time shift between envelopes. Zeros occur at: k/Nf_(s),k=1,2, . . . ,N−1 and at (2k−1)/2(N−1)f_(s), k=1,2, . . . ,N−1. CI cansupport N orthogonal users (or channels). If additional users or signalsneed to be accommodated, CI provides N−1 additional positions to placesignals.

A CI signal centered at time τ is orthogonal to the CI signal centeredat time t₁ whenever the difference between τ and t₁ is Δt=k/Nf_(s),k=1,2, . . . ,N−1. This enables CI waveforms to represent informationsymbols located sequentially in time without creating inter-symbolinterference. The superposition signal 110D shown in FIG. 1B representsa sum of the orthogonally positioned superposition signals 110A, 110B,and 110C.

An offset in the time domain corresponds to linearly increasing phaseoffsets in the frequency domain. A CI signal with a time offsetτ=k/Nf_(s) is equivalent to a CI carrier set with carriers 1 to N havingphase offsets:

{ϕ ₁ϕ₂, . . . , ϕ_(N)}={0, 2πk/N, 2·2πk/N, . . . , (N−1)·2πk/N).

Orthogonality between CI signals can be understood as an appropriatetime separation τ∈{k/f_(s), k=1, 2, . . . , N−1} between superpositionsignals, or as carriers of each carrier set coded with a differentpolyphase spreading sequence:

f(ϕ)={e ^(jθ1) , e ^(jθ2) , . . . , e ^(jθN) }={e ^(j0) , e ^(j2πk/N) ,. . . , e ^(j(N−1)·2πk/N)}

with respect to values of k=0, 1, . . . , N−1.

A set of quasi-orthogonal signals can be determined from non-orthogonaltime offsets that minimize the mean-squared value of the interferencebetween the quasi-orthogonal signals. This criteria is satisfied bymultiples of a time-offset value Δt=1/(2Nf_(s)). FIG. 1C shows a firstset of N orthogonal signals 110D represented in time by:

{t ₁ , t ₂ , . . . , t _(N−1)}={1/f _(s), 2/f _(s), . . . , (N−1)//f_(s)}.

A second set of N orthogonal signals 110D′ is represented in time by:

{t′ ₁ , t′ ₂ , . . . , t′ _(N−1)}=1/(2Nf _(s))+{1/f _(s), 2/f _(s), . .. , (N−1)//f_(s)}.

The first set of signals 110D is quasi-orthogonal to the second set110D′ and results in a minimal amount of interference, as shown in FIG.1D.

This result can also be expressed in terms of carrier phase offsetsusing the equivalence between shifts in the time domain and phaseoffsets in the frequency domain. A first set of N orthogonal signals isrepresented in phase by N complex spreading codes:

f ₁(ϕ)={e ^(jϕ1) , e ^(jϕ2) , . . . , e ^(jϕN) }={e ^(j0) , e ^(j2πk/N), . . . , e ^(j(N−1)·2πk/N)}

A second set of N orthogonal signals is represented in phase by Ncomplex spreading codes:

f ₂(ϕ)={e ^(jϕ′1) , e ^(jΔ′2) , . . . , e ^(j(0+Δϕ)) , e ^(j(2πk/N+Δϕ)), . . . , e ^(j((N−1)·2πk/N+Δϕ))}

where Δϕ=π/N.

The superposition signal 110D in FIG. 1B can be thought of as asuperposition of complex-weighted carriers in a carrier set 105D or asum of the superposition signals 110A, 110B, and 110C. The carrier set105D represents a sum of the carrier sets 105A, 105B, and 105C. Thecomplex amplitudes of carrier set 105D can be characterized by acomplex-weight vector w=[w₁, w₂, . . . , w_(N].) Each value w_(n) of theweight vector w corresponds to a particular carrier frequency f_(n). Thevalues w_(n) can be derived from a complex addition of carriers in thecarrier sets 105A, 105B, and 105C. The values w_(n) can be derived fromsumming complex numbers representing the magnitude and phase of eachcarrier in the carrier sets 105A, 105B, and 105C.

CI signals demonstrate both excellent frequency resolution and excellenttime resolution. A CI signal is composed of multiple narrowband carriersthat allow it to be resolved into its frequency components. Whenobserved in the time domain, a basic CI signal is very narrow, enablingit to be easily separated from other CI signals and to resolve thechannel's multipath profiles.

Because the period and width of the pulse envelope depends on theamplitudes, relative phases, and frequency separation of the CIcarriers, the frequency of each carrier may be changed without affectingthe pulse envelope as long as the amplitudes, relative phases, andfrequency separation are preserved. Thus, frequency hopping andfrequency shifting of the carriers does not affect the temporalcharacteristics of the superposition signal, such as superpositionsignal 110A. Tapering the amplitude distribution of the CI carriersbroadens the main-lobe width and reduces the amplitude of the sidelobes.

A CI signal has a number of carrier signals that may each have abandwidth that is less than the coherence bandwidth of the communicationchannel. The coherence bandwidth is the bandwidth limit in whichcorrelated fading occurs. The total bandwidth of the CI signalpreferably exceeds the coherence bandwidth.

CI carriers corresponding to any particular user, channel, or datasymbol may be spaced in frequency by large amounts to achieve a largesystem bandwidth relative to the coherence bandwidth. In this case, CIuses frequency to achieve uncorrelated fading However, any diversityparameter or combination of diversity parameters may be used to achieveuncorrelated fading over the system bandwidth, or even betweenindividual carriers.

The system bandwidth of a group of CI carriers may be selected relativeto the coherence bandwidth of one or more subchannels, such as spatialsub-channels. Carriers that are closely spaced in frequency may haveuncorrelated fading if they are transmitted from different locations orhave different degrees of directivity. CI carriers transmitted fromdifferent locations may have different fades over each spatialsub-channel and therefore, can benefit from diversity combining at areceiver (not shown).

Phase shifts applied to an n^(th carrier to separate a k) ^(th) channelfrom adjacent channels are given by:

ϕ_(kn) =πknf _(s)(Δt)+ϕ^(o) _(kn) =πkn/N+ϕ ^(o) _(kn)

where ϕ^(o) _(kn) is an initial phase-offset corresponding to the n^(th)carrier and the k^(th) channel. The values of At depend on whether thechannel spacing is orthogonal or quasi-orthogonal.

Although FIG. 1A and FIG. 1B illustrate an in-phase superposition ofcarrier signals, this example can be extended to other superpositions ofCI. For example, the time offset Δt (and the corresponding carrier phaseshifts ϕ_(kn)) for adjacent channels may be applied to CIimplementations that do not have in-phase superpositions. The timeoffsets Δt (and thus, the phase shifts Δ_(kn)) derived in this case arealso relevant to CI implementations that process the received carriersseparately. When each carrier is processed separately, phase-offsetcoding (in addition to the phase offsets ϕ_(kn) used to separatechannels) may be used to reduce or minimize the peak of thesuperposition signal.

The carrier sets 105A, 105B, and 105C have phase offsets correspondingto a pulse-width duration. However, any type of orthogonal (e.g.,non-overlapping) or quasi-orthogonal (e.g., overlapping) spacing may beprovided. Carrier sets having quasi-orthogonal (or non-orthogonal)spacing may be processed with multi-user (or multi-channel) detectiontechniques or with any other type of interference-suppression technique.

FIG. 1A and FIG. 1B illustrate several levels of signal decompositionthat reduce a complex time-domain signal into simple components. Thetime-domain pulses may be scaled and positioned to produce apredetermined time-domain signal indicative of an information signal,coding, and at least one transmission protocol. Multiple frequencycomponents may be weighted to produce an information signal havingpredetermined time-domain characteristics. Similarly, multiple frequencycomponents that comprise the pulses may be selected and weighted toimpart predetermined characteristics to the pulses. The scale of thecomponents selected for signal processing can be selected to provide adesired granularity for the information architecture.

Modulation of the pulses, the carriers, or both may be performed overthe duration of the signals shown in FIG. 1A and FIG. 1B. Carriermodulation may be performed over a pulse-repetition period, a pulseduration, or any multiple or fraction of either. In some cases, guardintervals, guard bands, and/or cyclic prefixes may be provided to CIsignals.

3. CI Codes

CI codes, as used herein, may include basic CI codes or advanced CIcodes. CI codes are based on phase relationships between orthogonalcarriers, such as illustrated by samples 220 to 225 shown in FIG. 2A.

Basic CI codes of the present invention can be derived from phaserelationships between orthogonal carrier frequencies. FIG. 2Aillustrates first and second orthogonal sinusoidal waveforms 201 and202. Each waveform 201 and 202 has an integer number of wavelengths overa particular symbol interval T_(s). The first waveform 201 frequency fis six cycles per symbol interval T_(s). The second waveform 102frequency f₂ is five cycles per symbol interval T_(s).

The samples 220 to 225 of waveform 202 are selected at intervals of Δt₁corresponding to periods 210 to 215 of waveform 201 over a symbolinterval T_(s)=6Δt₁. In this case, the waveforms 201 and 202 are alignedin phase at times t=0 and t=T_(s). At t=Δt₁, sample 221 occurs at ⅚ ofwaveform 202 period Δt₂. Each sample 220 to 225 can be represented by avalue on a unit circle in the complex plane. For example, FIG. 3A showsa complex-plane representation of samples 220 and 221.

Since the sampling frequency f₁ exceeds the frequency f₂ of the sampledwaveform 202, the phase shift of each successive sample 220 to 225 fallsshort of a full cycle of waveform 202. The waveforms 201 and 202 areorthogonal due to selection of an appropriate symbol interval T_(s) thatcauses the samples 220 to 225 to be distributed uniformly across theunit circle in the complex plane, as illustrated by FIG. 4A. The samplevalues 220 to 225 cancel when they are summed.

FIG. 2B illustrates a first waveform 201 sampled at intervals 230 to 235relative to a sampling frequency f₂ of a second waveform 202. A symbolinterval is expressed by T_(s)=5Δt₂. Each sample 240 to 244 correspondsto a phase shift that is greater than a full cycle of waveform 201, asillustrated by FIG. 3B. The orthogonality of the waveforms 201 and 202ensures that the samples 240 to 244 are distributed uniformly around theunit circle in the complex plane, as shown in FIG. 4B. Samples 240 to244 collected over a symbol interval T_(s) cancel when summed.

FIG. 4C shows a normalized complex-plane representation of samples(collected at a sampling rate f_(sample)f_(n)) of a desired waveformhaving a frequency f_(n). Since f_(sample)=f_(n), the samples alwaysoccur on the same part of the unit circle in the complex plane. Thus,the samples sum constructively. In this example, the samples occur atthe peaks of the desired waveform and thus, occur on the real axis inthe complex plane. The number of samples N_(s) per symbol interval T_(s)is expressed by:

N _(s) =f _(sample) T _(s)=(f _(o) nf _(s))/f _(s)

The number of samples per waveform period (1/f_(n)) is 1.

Nearby waveform frequencies f_(n±n′) can be expressed as:f_(n±n′)=f_(o)+(n±n′)f_(s). The number of samples per period of a nearbywaveform can be expressed as:

$N_{n \pm n^{\prime}} = {\frac{f_{n \pm n^{\prime}}}{f_{sample}} = {1 \pm \frac{n^{\prime}f_{s}}{\left( {f_{o} + {nf}_{s}} \right)}}}$

In the complex plane, the sampled values shift by an amount:

$\varphi_{n \pm n^{\prime}} = {{\pm \frac{n^{\prime}f_{s}}{\left( {f_{o} + {nf}_{s}} \right)}}2\pi \mspace{14mu} {radians}}$

N_(s) samples collected throughout the symbol interval T_(s) aredistributed uniformly on a unit circle in the normalized complex planeunless f_(n±n′) is an integer multiple off f_(n). The case in whichf_(n±n′)=mf_(n) (where m is some integer) can be avoided byappropriately frequency converting the received signal(s) and/or thesampling rate to ensure that the vector sum of the samples is zero.

CI codes can be used as direct-sequence codes, multicarrier codes (e.g.,MC-CDMA), etc. Applications of CI codes can be extended to anyapplication of conventional binary direct sequence codes, including, butnot limited to, spread spectrum, multiple access, channel coding,encryption, and interference mitigation. CI codes may be applied acrossany set of orthogonal or quasi-orthogonal diversity-parameter values orsubspaces.

Basic CI codes can be generated from phase relationships indicated byvector precession in the complex plane, such as shown in FIG. 4A. CIcoding can be applied to circular, elliptical, and linear polarization.CI polarization codes may be based on vector precession in a two- orthree-dimensional polarization plane. Advanced CI codes may be based onbasic CI polarization codes. Similarly, vector rotation in a plane or ahigher-dimension field of orthogonal bases may be used to generate basicand/or advanced CI codes. The basic family of CI codes is generated froman M×M matrix of elements having phases ϕ_(mn) described by:

ϕ_(mn)=2πmn/M+2πf _(o) m/f _(s) M,

where m and n are row and column indices, respectively. M may have anypositive integer value. The second term in ϕ_(mn) is an optional phaseshift applied to all terms in a row. The phase-shift ϕ_(mn) maycorrespond to a carrier frequency offset f_(o) and a sub-carrierseparation f_(s). A basic CI code c_(m) of length N can include a row orcolumn vector consisting of terms:

$c_{m} = {e^{{im}\; \varphi^{\prime}}{\sum\limits_{n = 0}^{N - 1}{e^{{imn}\; \varphi}\hat{n}}}}$

where ϕ=2π/M and ϕ′=2πf_(o)/f_(s)M.

Some of the CI codes are complex-conjugate pairs. For example,correlations between CI codes are expressed by the followingrelationship:

${corr}_{m,m^{\prime}} = {\left( \frac{1}{M} \right)e^{{i{({m + m^{\prime}})}}\varphi^{\prime}}{\sum\limits_{n = o}^{M - 1}e^{{{in}{({m + m^{\prime}})}}\varphi}}}$

The correlations are non-zero for (m+m′)=M.

CI codes may have polyphase and/or multi-magnitude values. A CI code setmay include one or more binary code vectors corresponding to at leastone conventional binary-phase code. In the case where CI codes includecomplex-valued chips, the real and imaginary parts may be impressed upondifferent orthogonal parameters. For example, a magnitude correspondingto a real value may be modulated on an in-phase carrier component,whereas a corresponding imaginary value may be modulated on aquadrature-phase carrier component.

Orthogonal components may include, but are not limited to, perpendicularlinear polarizations, left-hand and right-hand circular or ellipticalpolarizations, orthogonal polarization-spin frequencies, subspaces(e.g., spatial, directional, temporal, phase, polarization, etc.),orthogonal frequencies, orthogonal time intervals, direct-sequencecodes, etc. Modulation may include phase modulation, amplitudemodulation, frequency modulation, polarization modulation, time-offsetmodulation, or any combination thereof.

Phase shifts corresponding to CI code chips may be impressed upon asingle carrier or onto multiple carriers. In one embodiment, phaseshifts are impressed relative to a transmitted or locally generatedreference phase. In another embodiment, differential phase modulation(DPM) is employed. In one embodiment, DPM is employed on a singlecarrier. In another embodiment, DPM is applied to a multicarriertransmission protocol.

In one embodiment, each phase shift is conveyed as a phase differentialbetween at least two carriers.

CI codes may be applied to ordinary direct-sequence (e.g., DSSS orDS-CDMA), MC-CDMA, OFDM, coded OFDM, Discreet Multitone, WavelengthDivision Multiplexing (WDM), ultra-dense WDM, Multi-tone CDMA,Multi-code spread spectrum, or any of the CI protocols. In the casewhere CI codes are used in a multicarrier transmission protocol,phase-shift coding may be accomplished in any of several ways. Eachcarrier may be phase shifted with respect to each chip of a CI code chipsequence. Each carrier may be modulated with respect to anysingle-carrier modulation scheme. Each carrier may be modulated with oneor more CI code chip encoded subcarriers. Each carrier may be providedwith at least two diversity parameters that are modulated to convey realand imaginary parts of CI codes chips.

Multicarrier signals may be defined by any set of substantiallyorthogonal diversity-parameter values. These diversity parameters mayinclude, without limitation, frequency, phase space, polarization(including linear, circular, elliptical) in two or three dimensions,mode, code (e.g., DS and/or CI), time, any type of subspace, and anycombination thereof.

Advanced CI codes can involve one or more types of processing applied tobasic CI codes. Some examples of advanced CI codes include matricesresulting from processing basic CI codes with a Hadamard-Walsh matrix,matrices derived from Hadamard-Walsh/CI matrices, and expanded CImatrices based on Hadamard-Walsh matrix expansion.

The basic CI codes can be combined (with each other or with otherdirect-sequence codes) to faun other families of polyphase and/orpoly-magnitude CI codes. In any set of CI codes, the chip sequences maybe truncated, appended, rearranged, concatenated, etc., to generateorthogonal or quasi-orthogonal chip sequences. Codes of similar ordifferent lengths may be concatenated. Different chip sequences may becombined in such a way that at least one chip sequence is interleavedwith chips from at least one other code.

CI code vectors may be multiplied by other code vectors including, butnot limited to, direct-sequence codes, complementary codes, and/or otherCI codes. Groups of CI code chips may be modulated (scaled and/orshifted) with respect to other code chips. A CI code may be overlayedwith a long code, a Hadamard-Walsh code, a Barker code, a Gold code, aKasami code, a Golay code, a CI code, or some other code. CI coding mayinclude multiple levels of coding wherein at least one set of code chipsmodulates at least one other set of code chips.

Basic CI codes form an orthonormal basis. New orthonormal bases can begenerated by linearly combining CI codes of a particular length. Moreadvanced permutations of CI codes may also be provided to formorthonormal bases. The orthonormal bases may be multiplied by code chipsof other sequences, such as Hadamard-Walsh, Gold, CI, etc.

Data symbols may be mapped to CI codes to provide channel coding. Forthe purpose of mapping, bi-orthogonal CI codes may be generated byincluding a code set multiplied by the value −1. CI codes may be used togenerate trans-orthogonal (e.g., simplex) codes. Quasi-orthogonalmapping may be performed by phase shifting or scaling the CI codes. Asecond set of orthogonal CI codes may be generated by rotating the phaseof a first code set by π/2, thus providing in-phase and quadrature CIcodes.

CI-coded symbols may be decoded by correlating a coded signal with acomplex-conjugate code. A received signal may be processed with an FIRfilter having coefficients set appropriately to decode a desired signal.The received signal may be sampled and summed. Optionally, samples ofthe received signal may be weighted prior to being summed to compensatefor any of various effects, such as channel distortions,transmitter-side encoding (e.g., to reduce PAPR), jamming, etc.Weighting may be performed with respect to one or more optimizationprocesses in which weights are adjusted with respect to at least onemeasurement, such as signal to noise, signal to noise plus interference,probability of error, BER, received signal power, etc.

The received signal may be phase shifted with respect to chip phases ofa decoding signal. If a received signal includes multiple samples perchip interval, the chip samples may be time shifted with respect to thechip phases of the decoding signal. The samples corresponding to eachchip may be cyclically shifted with respect to a decode chip sequence.Subsequent processing, such as sampling, adding, comparison, and/ordecision making (hard and/or soft) may be performed to evaluate datasymbols measured after the decoding process.

FIG. 5A shows a set of 16 octonary code vectors C(n) resulting frommultiplying an 8×8 basic CI code matrix CI_(8×8) by rows of an 8×8Hadamard-Walsh matrix HW_(8×8). An 8×8 matrix resulting from a productof a matrix CI_(8×8) by a row of matrix HW_(8×8) includes twobinary-phase 8-chip codes (which correspond to rows of matrix HW_(8×8)),two quaternary-phase code vectors, and four octonary-phase code vectorsincluding two complex-conjugate pairs. The 16 code vectors C(n) areselected from octonary-phase vectors in matrices resulting from productsof vectors of HW_(8×8) with CI code matrix CI_(8×8).

FIG. 5B shows auto correlations and cross correlations of the 16octonary codes C(n) shown in FIG. 5A. The correlation relationships maybe used to choose orthogonal or quasi-orthogonal code sets from thecodes C(n). For example, the codes C(1), C(1)*, C(2), C(2)*, C(4),C(4)*, C(7), and C(7)* form an orthogonal eight-code set. The code pair{C(1), C(1)*} has zero cross correlation with C(2), C(2)*, C(4), C(4)*,C(7), and C(7)* and thus, can be used with these codes to provideorthogonal code sets. Code C(1) has a non-zero cross correlation withcodes C(1)*, C(5), and C(6)*. Thus, an orthogonal set may include codesC(1) and C(5), and exclude codes C(1)* and C(6)*. The codes C(3), C(3)*,C(5), C(5)*, C(6), C(6)*, C(7), and C(7)* form another orthogonaleight-code set. Codes C(7), C(3), C(8), C(4), C(1), C(5), C(2), and C(6)form yet another orthogonal eight-code set. Many other code sets,including quasi-orthogonal codes, are possible.

Orthogonal and quasi-orthogonal code sets may be implemented separatelyor simultaneously. Code sets may include combinations of different M-arypolyphase codes. An M-ary code set may include codes with a code length(i.e., number of code chips) that is less than or greater than M. Codesets may include numbers of codes that are less than or greater than thecode lengths. Code sets may include same-length and/or different-lengthcodes.

Although basic CI codes and one family of advanced CI codes aredescribed herein, many other implementations of coding based on CI areclearly anticipated. CI code sets may be selected or manipulated toprovide cross-correlation values that are shifted by π/2. CI codes maybe used to generate bi-orthogonal and/or trans-orthogonal CI code sets.CI codes may include linear combinations of other CI codes. CI codes maybe derived from Hadamard-Walsh matrix expansion, code concatenation,code interleaving, code superposition, and/or weighted codesuperposition wherein weights are applied to one or more code chips. ACI code may include at least one set of CI matrix elements, such as arow, a column, a diagonal, and/or matrix elements selected with respectto some predetermined pattern.

CI code chips may be cyclically shifted, swapped, or otherwisere-ordered. CI codes may be implemented as multi-level codes with one ormore codes that are not necessarily CI codes. Multiple codes includingat least one CI code may be interleaved. CI codes may be interleavedwith same length or different length codes. CI codes may be implementedin block coding, convolutional coding, turbo coding, any other form ofchannel coding, encryption, multiple-access coding, spread-spectrumcoding, peak-power mitigation, etc. CI codes may be implemented withorthogonal coding, quasi-orthogonal coding, bi-orthogonal coding,trans-orthogonal coding, or any combination thereof. CI codes may begenerated by convolving at least one set of CI codes with at least oneother set of codes, including one or more of the following: CI codes,binary direct-sequence codes, channel codes, spreading codes,multiple-access codes, etc. CI codes may be provided with one or moreparity-check symbols formed from linear combinations of data symbolsand/or code chips.

FIG. 6A illustrates basic components of a CI-code generator 603. ACI-symbol generator 609 generates a plurality of CI symbols that arecoupled to a symbol combiner 610. The symbol combiner 610 groups the CIsymbols to generate one or more CI codes.

A CI-symbol generator, such as the CI-symbol generator 609, includes anyalgorithm, system, or device adapted to generate a plurality of CIsymbols. CI symbols may include basic CI symbols. CI symbols may bediscreet-valued or continuous-valued numbers or functions. CI symbolsmay be values derived from at least one invertible transform function,such as a Fourier transform, a Laplace transform, a Walsh transform, awavelet transform, etc. CI symbols may include linear combinations ofother CI symbols, linear combinations of CI symbols with other codesymbols, CI symbols modulated with code sequences from a predeterminedcode set including one or more of the following: spread-spectrum codes,multiple-access codes, channel codes, encryption codes, multi-levelcodes, compression codes, hybrid codes, invertible-transform codes, andCI codes.

A CI symbol combiner, such as the symbol combiner 610, includes anyalgorithm, system, or device adapted to group CI symbols to generate atleast one CI chip sequence. A symbol combiner may append, concatenate,interleave, shift, puncture, or re-order one or more symbol sets. Asymbol combiner may combine CI symbols with other symbols. A symbolcombiner may provide a CI chips sequence with at least one parity-checksymbol.

FIG. 6B illustrates a CI transmitter adapted to generate at least oneCI-coded information signal. A CI encoder 600 encodes at least one inputinformation signal relative to at least one CI code produced by a CIcode generator 603. CI coded information signals are optionally coupledto a transmission system 602 that may include a pre-transmissionprocessor (not shown).

FIG. 6C illustrates basic components of a CI decoder that include a CIcode generator 603 and a coherent combiner 605 adapted to decode atleast one CI-encoded signal with respect to at least one code generatedby the CI code generator 603. Optionally, the decoder may be coupled toa front-end receiver processor 604 that provides the at least oneCI-encoded signal to the decoder.

Channel coding provides signal transformations that are designed toimprove communication performance by enabling transmitted signals tobetter withstand the effects of various channel impairments (e.g.,noise, fading, interference). CI channel coding may include waveformcoding and/or structured sequences. CI waveform coding (such as M-arysignaling, orthogonal coding, bi-orthogonal coding, trans-orthogonalcoding, etc.) transforms waveforms to make them less subject to error.CI-structured sequences transform a data sequence into one or moresequences having structured redundancy. Redundant bits are used fordetecting and/or correcting errors.

CI coding may include replacing a data set with an orthogonal codewordset. In one embodiment, a CI coder may multiplex multiple coded datasymbols together by providing an orthogonal codeword set. A CI codewordset may be selected in which each codeword vector has zero projectiononto all other CI codeword vectors except for its complex conjugate. Adecoder may include multiple matched filters (or equivalent systems oralgorithms) that output zero unless a corresponding encoded data symbolis received.

FIG. 7 illustrates a relationship between CI symbol values w_(n) anddata symbols s_(n). CI code chip values are arranged in columns withrespect to phase spaces, such as phase space (column) 701. A phase spacemay be analogous to a pulse position. The phase spaces (e.g., pulsepositions) may be orthogonal or quasi-orthogonal. Thus, the number of CIsymbols w_(n) may differ from the maximum number of data symbols s_(n).Each data symbol value s_(n) is impressed upon a phase space such thateach set of CI code chip values in that phase space expresses the valueof the corresponding data symbol s_(n). Each code chip value isanalogous to a complex weight applied to a particular CI carrier. Asuperposition of these carriers produces a CI waveform (e.g., pulse)bearing the data symbol value s_(n).

A CI superposition waveform bearing multiple data-symbol/pulse-positioncharacteristics can be created by applying weights to CI carriers thatcorrespond to sums of carrier weights for eachdata-symbol/pulse-position. Similarly, each CI symbol, such as symbolw₂, corresponds to a summed row of data-bearing CI code chips, such asrow 703. The code chips may be transmitted over multiple time intervals,carrier frequencies, polarizations, and/or other orthogonal diversityparameter values.

Decoding may include any appropriate inverse of the coding operationrepresented by FIG. 7. For example, to extract an n^(th) data-symbolvalue s_(n) from a vector of received CI symbol values w, the complexconjugate of a vector of the n^(th) phase space (or CI code) valuesw_(n) may be correlated with the received CI symbol vector w. Equivalentdecoding processes may be performed. The decoding process may beperformed with respect to one or more combining techniques, such as, butnot limited to, MMSE, EGC, maximum likelihood combining, or anycombination thereof. Decoding may include turbo decoding.

FIG. 8A illustrates basic components of a CI coding system and a CIdecoding system. A data symbol stream 801 is processed by a CI symbolgenerator 820 that outputs a plurality of CI symbol values w_(n)representing a coded version of the data symbols s_(n). The symbolsw_(n) may be interleaved by an optional interleaver 804 prior to beingprepared for transmission into a communication channel 899 by apre-transmission processor (not shown) in a transmission system 805. Thesymbols w_(n) are typically multiplexed onto one or morediversity-parameter spaces prior to transmission.

A receiver system 806 couples transmitted signals from the channel 899,and a front-end receiver processor (not shown) performs any necessaryprocessing, such as filtering, amplification, demultiplexing,de-spreading, decoding, and/or beam forming, prior to outputting an IFor baseband digital signal. Optionally, channel compensation 807 may beperformed to mitigate effects of channel distortion and/or interference.Any necessary de-interleaving processes 808 may be performed prior toprocessing by a CI symbol decoder 830. The decoder 830 processesreceived CI symbols w′_(n) to produce data-symbol estimates 801′. Thedata-symbol estimates 801′ may be output to additional signal-processingsystems (not shown).

The CI Symbol Generator 820 converts a predetermined number of inputdata symbols s_(n) to a plurality of CI code symbols w_(n). Thisconversion may involve summing information-modulated CI code chips. Afirst step in a CI symbol generation process may include generating codechips and/or acquiring code chips stored in memory or received from aninput data stream. Code chips may be generated from a reduced set (e.g.,an orthonormal basis) of code chips or code vectors.

A second step in a CI symbol generation process involves impressing atleast one data symbol s_(n) onto at least one set of code chips. Thecode chips may be multiplied, phase shifted, modulated, or otherwiseimpressed with data symbol values s_(n). The code chips may represent aphase space, such as a pulse position. Optionally, the code chips may beprovided with phase offsets, such as for crest-factor reduction orencryption.

A third step in a CI symbol generation process involves combining thecode chips to produce one or more CI code symbols w_(n). FIG. 7illustrates how rows of information-modulated CI code chips are summedto produce CI code symbols w_(n). Predistortion may be provided applyingchannel-compensation weights to the CI code symbols w_(n).

The decoder 830 processes received CI symbols w′_(n) to producedata-symbol estimates 801′. A first step in a CI decoding methodincludes generating code chips and/or acquiring code chips stored inmemory or received from an input data stream. Code chips may begenerated from a set of orthonormal codes or a subset of chipscomprising one or more orthonormal codes.

A second step in a CI signal processing method includes combining orcorrelating at least one vector of the code chips with a vector of thereceived data symbols w′_(n). A correlation process may include a scalarmultiplication between the code chip vector and the received data symbolvector followed by combining (e.g., integrating) the products. Anotherembodiment of correlation includes adding together selected samples overa predetermined symbol interval T_(s). Additional processing may beperformed to produce estimates of the transmitted data symbols.

The decoder 830 may perform various types of combining, such as weightedcombining as part of an MMSE, EGC, maximal likelihood, or any otherperformance-based optimization process. The decoder 830 may performchannel compensation. The decoder 830 may include a front-end receiverprocessor (not shown).

The bandwidth requirements for bi-orthogonal CI codes are half of therequirements for comparable orthogonal codes. Bi-orthogonal codes haveslightly better performance over orthogonal codes because antipodalsignal vectors have better distance properties than orthogonal signals.Trans-orthogonal (e.g., simplex) codes, when compared to orthogonal andbi-orthogonal codes, require the minimum SNR for a particular symbolerror rate. Channel codes may be overlaid onto multiple-access codes.Depending on the processing gain of the multiple-access codes, channelcoding may not require additional bandwidth.

FIG. 8B shows a system diagram of a CI transceiver. An informationsource 851 provides data symbols to a CI coder/interleaver 852. Amodulator 853 modulates the coded symbols onto one or more carriers thatare transmitted by a transmitter 805 into a communication channel 899.The channel 899 may be characterized by AWGN and/or multipath. Otherchannel distortions may be considered. A receiver 806 couples thetransmitted signals out of the channel 899. A demodulator 863 retrievessymbols from the received signal. A CI decoder/de-interleaver 862decodes (and de-interleaves, if necessary) the received symbols intoinformation symbols that are optionally processed in an informationprocessor or sink 861.

In one embodiment, the coder 852 maps data symbols to CI code wordsusing a look-up table. In another embodiment, the CI code words aregenerated with respect to each data symbol. Codeword generation may beperformed with a CI code generation matrix G. CI codes of a given set ofCI code words may be constructed from a combination of linearlyindependent code vectors that form the CI code generation matrix G.

Although code generation is described with respect to basic CI codes,orthonormal basis vectors and a corresponding CI code generation matrixmay be constructed for advanced CI codes. Each code in a basic CI codeset can be defined by a different number of full rotations in thecomplex plain. For example, an orthonormal basis for a set of N=64 basicCI codes can be defined by the CI code generation matrix:

$G = \begin{bmatrix}{C\left( {{rotations} = 1} \right)} \\{C\left( {{rotations} = 2} \right)} \\{C\left( {{rotations} = 4} \right)} \\{C\left( {{rotations} = 8} \right)} \\{C\left( {{rotations} = 16} \right)} \\{C\left( {{rotations} = 32} \right)}\end{bmatrix}$

where C(rotations=m), m=0,1, . . . ,N−1, is a code vector correspondingto:

C(m)=e ^(imϕ′)(1,e ^(imϕ) ,e ^(i2mϕ) , . . . ,e ^(i(N−1)mϕ))

Since this basic CI code set is totally defined by G, the coder 852needs to store only k rows of G instead of 2 ^(k) vectors of the CI codematrix. Furthermore, since the first half of each row vector C(m) of Gis the same as the second half (except C(1)'s first and second halvesdiffer by a factor of −1), the coder 852 and decoder 862 need only storeone half of each row vector C(m).

A CI receiver may perform error detection using any of severaltechniques. Symmetry relationships between the first and second halvesof a received code can be exploited to determine whether an erroroccurred. Other relationships between code symbols may be used toprovide error detection and/or correction. For example, adjacent CI codesymbols (except for the all-ones code) are typically not identical.Depending on the code, the values of adjacent code symbols change in apredetermined way. For example, adjacent code chips of an m^(th) basiccode C(m) differ by e^(imϕ).

A parity-check matrix H (defined by the equation, GH^(T)=0) can be usedto test whether a received vector is a member of a codeword set. Thedecoder 862, upon detecting an error, may perform forward errorcorrection and/or request a retransmission. Preferably, the decoder 862estimates the transmitted code vector using some optimizing strategy,such as the maximum-likelihood algorithm. The receiver may eraseambiguous signals. The decoder 862 may implement error correction tocorrect erasures and/or errors.

It is preferable that the coder 852 select codes that maximize theHamming distance between codes. An advantage of using polyphase codes isthat they provide a superior Hamming distance compared to binary codes.For example, (n,k)=(8,3) binary code has an n-tuple space of2^(n)=2⁸=256 binary words, of which 2^(k)=2³=8 are code words. Anoctonary-phase (m=8) (8,3) code has an n-tuple space of 2 ^(mn)=2⁶⁴octonary words. The fraction of words that are code words decreasesdramatically with increasing values of m. When a small fraction of then-tuple space is used for code words, a large Hamming distance can becreated.

CI codes may be processed as cyclic codes, which are described in manyprior-art references, such as B. Sklar, Digital Communications,Fundamentals and Applications, Prentice-Hall, Inc., New Jersey, 1988.For example, components of a CI code vector C=(C₀, C₁, . . . , C_(N−1))can be treated as coefficients of a polynomial U(X), as follows:

U(X)=u ₀ +u ₁ X+u ₂ X ² +. . . +u _(N−1) X ^(N−1)

where X=e^(i2πnk/N), where k is the order of the code: k=0,1, . . .,N−1. Well-known cyclic code processing may then be performed.

4. CI Networks

FIG. 9A illustrates a tree network that may be implemented in aspects ofthe present invention. Transmissions passed to one or more nodes in thenetwork may be branched off, or routed, to a plurality of nodes. Routingmay include processing any combination of network addresses conveyed inheaders and network addresses conveyed by codes (e.g., spreading codes,multiple-access codes, channel codes, etc.).

Network addresses may provide routing information and/or directions. Forexample, multiple addresses may convey one or more paths between asource node and a destination node. Various types of control informationmay be included in a code. For example, certain codes may conveypriority information, identify the type of data payload, and/orotherwise tag the transmission.

FIG. 9B illustrates a network design that permits a plurality ofcommunication paths to each node. Multiple network connections between asource node and a destination node may be provided for redundancy.Alternatively, each path may be selected based on one or more criteria,such as channel conditions and load balancing.

FIG. 9C illustrates a network design adapted to provide array processingperformance advantages. A plurality of nodes 926, 927, 902, 920, 921,and 922 are adapted to provide complex-weighted transmissions to atleast one destination node, such as nodes 931 and 932. For example, adata sequence addressed to node 931 is routed to nodes 926, 927, 902,920, 921, and 922, which provide appropriate weights to the datatransmission to generate a phase front 941 that converges at thedestination node 931. Similarly, appropriate delays or complex weightsmay be provided to transmissions to produce a coherent phase front 942that converges at destination node 932. Signals received by the nodes926, 927, 902, 920, 921, and 922 may be combined with respect to anycombining technique, including optimal combining.

Nodes in a wireless network may generate weighted transmissions (orprocess received signals) to perform various types of array processing.Individual nodes may include one or more transceiver (e.g., antenna)elements. Array-processing operations may include combinations of localand global processing. For example, diversity combining may be performedat each multi-element node and signals from each node may be combined ina central processor to perform sub-space (i.e., directional) processing.Other combinations of local and global processing may be employed. Arrayprocessing may include space-time processing, space-frequencyprocessing, beam forming, null steering, blind-adaptive processing, longbaseline interferometry, frequency-diversity interferometry, etc. Arrayprocessing may be performed to achieve any combination of sub-spaceprocessing (i.e., increased capacity) and diversity benefits in (i.e.,improved performance). Selection of transmitting and receiving nodes inan array-processing network can be adapted to changing node positions,network loads, throughput requirements, user services, bandwidthavailability, frequency-reuse requirements, channel conditions, etc.

FIG. 9D illustrates a concentric ring network configuration in which abase station 900 or access point provides direct or indirectcommunication links to a plurality of subscriber units 901 to 935arranged in a plurality of concentric-ring regions 951 to 953.Subscriber units 901 to 906 in region 951 are adapted to route signalsto one or more subscriber units 921 to 935 in one or more regions, suchas region 953. Similarly, subscriber units 911 to 918 in region 952 maybe adapted to route signals to subscribers in other regions. In someapplications, one or more subscribers may be adapted to route signals toat least one other subscriber in the same region.

Region shapes and sizes may be adapted to numbers of users and/or thegeographical distributions of the users. Similarly, regions may beadapted to balance network loads. For example, subscriber powerconsumption and processing requirements associated with routing signalsthrough subscribers near the base 900 can be mitigated by distributingrouting operations over a larger number of subscribers. Thus,subscribers in regions 951 and 952 perform routing associated with adirect transmission from and/or to the base 900. Similarly, the numberof subscribers in primary arteries of tree networks (or other networks)can be increased. Routing functions can be assigned to subscribers basedon subscriber location, subscriber load, channel conditions, and networkload. The network configuration illustrated in FIG. 9D may be integratedwith other network architectures, such as tree configurations, orotherwise adapted to geographical distributions of subscribers and othernetwork transceivers.

FIG. 9E illustrates a network configuration adapted to the geographicdistribution of a plurality of subscribers 921 to 926 and 931 to 936located along a roadway. In this case, there are two routing paths 961and 962 provided by subscriber routing. Network configurations,including transmission paths, may be adapted to subscriber distributionsand channel conditions. For example, urban channel environments aretypically characterized by a waveguide grid. Thus, routing paths may beprovided with a grid architecture in urban areas.

A transmission may include multiple levels of coding intended to bestripped off at each node along a predetermined path to a particularaddress. FIG. 9F illustrates three nodes 901, 902, and 904. The firstnode is adapted to decode a one-rotation basic CI code by applyingcomplex-conjugate decoding of the one-rotation code. A basic CI codec_(m) characterized by m rotations (m<N) is expressed by the followingequation:

$c_{m} = {e^{{im}\; \varphi^{\prime}}{\sum\limits_{n = 0}^{N - 1}{e^{{imn}\; 2{\pi/N}}\hat{n}}}}$

The complex-conjugate decoding essentially unwinds the code. Similarly,nodes 902 and 904 are adapted to decode two-rotation and four-rotationcodes, respectively. For simplicity, the rotations are provided in acommon predetermined direction.

In one aspect of the invention, each node splits a received signal intoat least two signals. At least one of the split signals is decoded atthe node to extract any information intended for that node. A node maybe associated with one or more addresses, or codes. At least one splitsignal is passed through the node without any decoding. Thus, node 901receives signals coded (or addressed) with one code rotation, node 902receives signals coded (or addressed) with two code rotations, etc.

In another aspect of the invention, a signal input to a node is notsplit prior to being decoded to extract any signals intended for thatnode. The decoded signal is then re-encoded with respect to the complexconjugate of the decoding operation. Thus, any unwinding associated withdecoding is reversed prior to re-transmission of the coded informationsignal. Optionally, a node transceiver may cancel or otherwise removesignals addressed to itself prior to re-encoding.

In yet another aspect of the invention, coded transmissions are codedwith respect to the intended path(s) to a predetermined address, thusobviating the need for splitting or re-encoding. For example, aninformation signal addressed to nodes 902 and 904 input to the firstnode 901 is encoded with a pair of basic CI codes having three rotationsand seven rotations, respectively:

$r_{{node}\; 901} = {\sum\limits_{n = 0}^{N - 1}{\left( {{{s_{2}(t)}e^{i\; 3n\; 2{\pi/N}}} + {{s_{4}(t)}e^{i\; 7n\; 2{\pi/N}}}} \right)\hat{n}}}$

Decoding at the first node 901 unwinds the coded signals by onerotation. The decode signal is characterized by C*(1), which is thecomplex conjugate of code C(1). Thus, node 901 passes a codedinformation signal to node 902 expressed by two-rotation andsix-rotation codes:

$r_{{node}\; 902} = {\sum\limits_{n = 0}^{N - 1}{\left( {{{s_{2}(t)}e^{i\; 2n\; 2{\pi/N}}} + {{s_{4}(t)}e^{i\; 6n\; 2{\pi/N}}}} \right)\hat{n}}}$

A sum of the decoded chips yields zero because there are no inputsignals coded with a single-rotation code. A sum of the chips generatedat node 901 is zero because the non-zero rotations cause the chip valuesto cancel.

Decoding with decode signal C*(2) at node 902 unwinds the coded signalsby two rotations. Thus, a sum of the decoded signal at node 902coherently combines chip values associated with signal s₂(t) and cancelschip values associated with signal s₄(t). Node 902 produces a codedinformation signal expressed by:

$r_{{node}\; 904} = {\sum\limits_{n = 0}^{N - 1}{\left( {{s_{2}(t)} + {{s_{4}(t)}e^{i\; 4n\; 2{\pi/N}}}} \right)\hat{n}}}$

The values s₂(t) may optionally be removed (such as by cancellation,dc-offset removal, etc.) prior to transmission to node 904. A nodetransceiver at node 902 may ensure non-zero chip values prior totransmission.

Coded signals received by node 904 are processed with acomplex-conjugate code C*(4) that unwinds the coded signal by fourrotations. The resulting decoded signal is expressed by:

$r_{{node}\; 904^{\prime}} = {\sum\limits_{n = 0}^{N - 1}{{s_{4}(t)}\hat{n}}}$

Decoding and summing the code chips at node 904 coherently combinessignal values s₄(t) associated with a four-rotation code C(4).

FIG. 9G illustrates a simple tree-style CI-based network. Nodes 901,902, and 904 are provided with decode signals corresponding to C*(1),C*(2), and C*(4), respectively. A branch node 903 employs a decodesignal C*(3) adapted to decode signals characterized by three rotationsin a predetermined direction. A signal addressed with basic CI codescorresponding to rotations of seven, three, and six are input to node901. Signals output by node 901 to node 902 correspond to rotations ofsix, two, and five. Node 902 provides a decode signal of C*(2) to itsinput signal. Thus, the input corresponding to two rotations is decodedand the resulting value is processed at the node 902. The resultingoutput signal(s) from node 902 is expressed by rotations as four, zero,three. The zero value may characterize a substantially null signalresulting from cancellation of the decoded signal at node 902.

Node 902 may provide a broadcast signal to nodes 903 and 904.Alternatively, node 902 may duplicate the signal four, zero, three andprovide a signal to each of the nodes 903 and 904. In some cases, node902 may be adapted to separate its input signal into a plurality ofcomponents relative to addresses. Each component may be forwardeddirectly to its intended node. In some cases, separate signals may beprovided via beam forming. In other cases, some form of multiple access,including header addresses, may be employed.

FIG. 9H illustrates a simple multipath CI-based network. Node 902 isprovided with coded signals (expressed in rotations as 2,5,6,3,4). Thevalue two is addressed to node 902. The values five and six areaddressed to nodes 903 and 904. A fourth node 906 receives transmissionsfrom nodes 903 and 904. Thus, values three and four characterize pathsthrough nodes 903 and 904, respectively, that are addressed to node 906.Signals received and decoded at node 906 may be combined coherently.Such combining may include optimal combining.

In some aspects of the invention, node 906 may be provided withadditional decode values (e.g., C*(5)) to enhance reception.Furthermore, two or more decode values (e.g., C*(6) and C*(5)) may beexploited in appropriate combinations to provide beam forming (orequivalent array processing) operations. Various combining operationsmay be performed to provide any combination of interference rejection,diversity enhancement, and sub-space processing (i.e., capacityenhancement).

FIG. 9I illustrates a plurality of nodes 901 to 905 and at least twocommunication paths. A first communication path includes nodes 902, 904and 905. A second communication path includes nodes 901, 903, and 905.In this case, the two paths illustrate communication to node 5.Alternatively communication paths may be provided indicatingcommunications from node 905.

Signals arriving from the first communication path are encoded with atleast one code c₁(n). Similarly, the signals arriving from the secondcommunication path are encoded with at least one code c₂(n). In variousapplications of the invention, additional communication paths (notshown) may be provided.

The codes c₁(n) and c₂(n) may be address codes or they may includeaddress codes. The codes c₁(n) and c₂(n) may be similar or different.Alternatively, the codes c₁(n) and c₂(n) may be separate (or different)from address codes. In some cases, address codes may be adapted toprovide additional coding or achieve other objectives, such as, but notlimited to, encryption, verification, authentication, identification,anti-jamming, and/or diversity benefits.

In one set of embodiments of the invention, redundant informationsignals or signals providing redundant information are routed along themultiple paths to the destination node 905. This can provide diversitybenefits. The codes c₁(n) and c₂(n) may include similar or differentchannel codes. Signals provided along the multiple paths may be decoded(if necessary) and coherently combined in a receiver at the node 905.Combining may include one or more optimal-combining techniques. Thenumber of transmission paths that are coherently combined isproportional to an effective processing gain of the combining process.Consequently, low-power information-bearing transmissions may beemployed over the multiple transmission paths. Signals received fromdifferent paths may be processed via soft-decision processing to provideconfidence measurements for symbol estimates and/or enhance channelcompensation and/or iterative decoding.

In another set of embodiments, each of a plurality of signals routedalong different paths to a given node may provide necessary keys (orequivalent information) necessary for decoding. For example, signalsrouted along a first path may provide a coded information signal to apredetermined destination. Signals routed along a second path to thesame destination may provide a decode sequence to decode the codedinformation signal. The codes c₁(n) and c₂(n) may include codes that arecomplex conjugates of each other. The first code c₁(n) may include apublic key and the second code c₂(n) may include a private key whereinthe two codes c₁(n) and c₂(n) contribute the necessary code keys fordecoding a coded information signal transmitted along the first and/orsecond paths, or along a third path. Various pluralities of codes,paths, and/or coded information signals may be employed.

The process of providing multiple decoder keys across multipletransmission paths may be part of an authentication and/or verificationprocess. The codes c₁(n) and c₂(n) may include channel-specific codesthat characterize the channel between at least one transceiver and thedestination node 905. The codes c₁(n) and c₂(n) may include channelcompensation. Consequently, a channel analysis of received signals atthe destination node 905 will indicate the likelihood that the signalswere transmitted from known nodes, such as nodes 903 and 904. Similarly,channel analysis may be employed to determine the local source node of agiven transmission. The codes c₁(n) and c₂(n) may include beam-formingweights.

In some aspects of the invention, channel estimation may be performed ona signal received from a transceiver attempting to access the network.Various location-finding processes (e.g., direction-of-arrivaldetermination, geo-location tracking, triangulation, etc.) may beimplemented to determine the transceiver's location relative to a set orrange of allowed locations. In some applications, identification ofunauthorized users may be combined with location finding.

FIG. 9J illustrates a node 902 used in a plurality of crossingcommunication paths. Nodes 901, 902, and 904 are part of a firstcommunication path. Nodes 911, 902, and 913 are part of a secondcommunication path characterized by at least one unique diversityparameter value. In this case, the communication paths are distinguishedby different carrier frequencies. Alternatively, communication paths maybe differentiated by code, polarization, subspace, time, phase,subspace, or any combination thereof.

Although basic CI codes are illustrated in the exemplary networkarchitectures, other types of codes (including, but not limited to,complex CI codes, Walsh codes, multi-code sets, multi-level (or stacked)codes, and/or codes derived from invertible transforms) may beimplemented in the examples shown, as well as in variations,adaptations, permutations, and combinations of the exemplary networkarchitectures. Network address codes may be employed for one or moreadditional functions, including, but not limited to, spread spectrum,multiple access, channel coding, and encryption. Network designs shownin the figures and described in the specification are intended to conveybasic principles and various aspects of the invention. These networkdesigns do not limit the scope of the invention. Consequently, variousnetwork designs may be considered as building blocks for complex networkarchitectures.

Network designs and other aspects of the invention may be combined withprior-art network designs, systems, devices, protocols, formats, and/ormethods. Such combinations are clearly anticipated and suggested.Aspects and embodiments of the invention may serve as portions ofnetworks. Network designs, systems, and/or methods of the invention maybe adapted to various types of networks, such as long-haul, short-haul,last-mile, local-area, metropolitan-area, sensor, RF-identification,tracking, ad-hoc, mobile radio, personal communication, cellular,airborne, air-ground, and/or satellite networks. Network architecturesof the invention may include one or more types of multiple access.Network architectures of the invention may include any combination ofaddressing, including address codes and packet headers containingaddresses.

FIG. 10A illustrates a multi-level cellular architecture that may beemployed by systems and methods of the present invention. At least onemacro-cell 1021 is subdivided into one or more micro-cells 1031. Variousmultiple-access techniques may be used to separate communications indifferent cells. For example, a predetermined code may be provided totransmissions within the macro-cell 1021. Macro-cell codes may beprovided for inter-cell multiple access or radio isolation. Micro-cellcodes may be provided for intra-cell multiple access. Codes applied totransmissions may implement additional network functions, such as spreadspectrum, encryption, authentication, channel coding, addressing, and/orinterference mitigation.

In some applications, multi-level codes may be implemented. In somecases, macro-cell codes may provide greater processing gain than themicro-cell codes. For example, macro-cell codes may consist of longcodes and micro-cell codes may consist of shorter channel codes and/ormultiple-access codes. Either or both micro-cell codes and macro-cellcodes may implement CI and/or CI-based coding. Coding may be implementedwith, or as part of, array processing.

FIG. 10B illustrates three cells 1021 to 1023 in a cellular network ofthe present invention. Each cell 1021 to 1023 employs a different longcode C_(L1) to C_(L3), respectively, to differentiate betweencommunications in adjacent cells. Each cell 1021 to 1023 providesintra-cell communications with codes C_(s1−N) to differentiate betweensubscriber units in each cell. Coding may include CI and/or CI-basedcodes. Additional multiple-access techniques may be employed to providefor inter-cell and intra-cell multiple access.

FIG. 10C shows a cellular architecture of the present invention thatincludes a plurality of cells 1021 to 1025 and a plurality of basestations 1001 to 1005 located on cell boundaries. The base stations 1001to 1005 may include spatially sectorized antennas to providecommunication to a plurality of cells. For example, base 1002 may beadapted to service users in cells 1021, 1022, and 1023.

The base stations 1001 to 1005 may be adapted to route coded informationacross multiple cells. For example, coded data and/or controlinformation is routed from base 1002 to base 1003. A coded signal may beduplicated or decomposed for routing to multiple bases or subscriberunits. For example, base 1003 transmits coded information to bases 1004and 1005. In some applications, subscriber units, such as subscriberunits 1011 and 1012 may be employed to route information between two ormore base stations. In any of the implementations of the invention,transmission paths through a network may be selected based on one ormore criteria, including transceiver availability, transceiverlocations, network loads, channel conditions, transmission-powerrequirements, etc.

FIG. 10D illustrates a cellular network of the invention including aplurality of cells 1021 to 1030, a plurality of base stations 1000 to1009, and a plurality of subscriber units, such as subscriber units 1061to 1063 and 1071 to 1073. In this case, the bases 1000 to 1009 arelocated inside each cell 1021 to 1030. Other cellular architectures maybe employed.

A base station (e.g., base 1000) may route information directly to otherbases (e.g., bases 1001, 1002, 1004, 1005, and 1006). Such directtransmissions paths are indicated by transmission paths 1041 to 1045. Adirect transmission path 1046 may be provided to a base (such as base1009) that is not adjacent to the originating base 1000. A transmissionbetween bases may be routed through intermediate bases. For example,base 1005 acts as a router for transmissions between base 1000 and bases1007 and 1008. Similarly, subscriber units (such as subscriber units1071 and 1072 may be employed as routers for communications betweenbases (e.g., bases 1000 and 1003), between subscribers, and/or betweenbases and subscribers.

5. CI Routing Systems

FIG. 11A illustrates a CI transceiver adapted to perform routing.Transmitted signals are received by a receiver system 1101 that outputsa baseband or IF signal. The receiver system 1101 performs RF and(optionally) baseband processes typically performed to convert an RFsignal to a baseband or intermediate frequency signal. For example, thereceiver system 1101 may perform channel selection, filtering,amplification, frequency conversion, and A/D conversion.

A CI decoder 1102 is adapted to decode the baseband signal relative toone or more address codes intended for the transceiver. The decoder 1102may select a signal relative to an address in a header prior todecoding. A signal processor 1103 may process the decoded signals priorto producing an output data stream. Signal processing may include one ormore signal-processing operations, including, but not limited to,quantization, channel decoding, multiple access decoding,demultiplexing, formatting, demodulation, channel estimation, channelcompensation, synchronization, filtering, error detection, errorcorrection, signal-quality analysis, multi-user detection, phase jittercompensation, frequency-offset correction, time-offset correction, etc.

A control system 1104 is adapted to select, adapt, or otherwise controlthe operation of one or more transceiver components. For example,channel estimates and/or signal-quality analysis performed by the signalprocessor 1103 may be processed in the control system 1104 to adaptdecoding performed by the decoder 1102. The control system 1104 mayprovide power-control information to the transmission system 1106. Forexample, power control may include mitigating the effects of near-farinterference. Channel selection may also be performed to mitigatenear-far interference. The control system 1104 may provide other typesof network control. For example, CI coding may be adapted by the controlsystem 1104.

A CI coder 1105 is adapted to process input data bits to produce a codedsignal that is coupled to a transmission system 1106. The transmissionsystem 1106 performs signal-processing operations typically performed toprepare a baseband signal for transmission into a communication channel.The transmission system 1106 may perform one or more processes,including, but not limited to, D/A conversion, modulation, filtering,amplification, frequency conversion, beam forming, etc.

Signals from the receiver system 1101 are coupled to a CI decoder 1112,which may include a bank of CI decoders. The decoder 1112 decodesreceived signals that are to be retransmitted. The decoded signals areprocessed in a signal processor 1113. The signal processor 1113 mayperform similar signal-processing operations as signal processor 1103.Additionally, the signal processor 1113 may perform duplication,addressing, signal removal, information insertion, re-routing functions,and/or transmitter 1106 control. Furthermore, the signal processor 1113may perform pre-processing operations prior to coding in a CI coder1115. The coder 1115 may include a CI coder bank. A control system 1114is adapted to select, adapt, or otherwise control the operation of oneor more of the transceiver components 1112, 1113, and 1115.

The control system 1114 and the coder 1115 may providechannel-compensation and/or beam-forming weights to the coded symbols.Such weights may be regarded as part of the routing process. Sincerouting decodes some signals that are not intended for the transceiver,the router components 1112, 1113, 1114, and 1115 are isolated from therest of the transceiver by a fire wall 1110.

Code division duplexing or cancellation division duplexing may beemployed to permit reliable reception while concurrently transmitting.Alternatively, other types of duplexing may be employed. Pseudo-randomtime, frequency, and/or phase codes are typically used to avoidself-jamming. However, CI codes and CI-based waveforms enable thefrequency-domain processing required for optimal performance in amultipath environment while providing data redundancy (i.e., channelcoding) needed to mitigate errors. Optionally, additional channel coding(e.g., block, convolutional, TCM, turbo, etc.) may be provided to CIwaveforms and/or CI coding.

FIG. 11B illustrates an alternative embodiment of a CI receiver adaptedto perform routing. Many of the system components shown in FIG. 11B aresimilar to components shown in FIG. 11A and thus, are identified bycorresponding reference numbers. A portion of the baseband (or IF)signal(s) produced by the receiver system 1101 is optionally processedin a processor 1119 prior to being coupled into the transmission system1106.

The processor 1119 may perform one or more baseband or IF processes,including, but not limited to, signal shaping, filtering,re-quantization, error detection, error correction, interferencemitigation, multi-user detection, amplification, up sampling, downsampling, frequency conversion, D/A conversion, AGC, symbol remapping,etc. The processor 1119 may be adapted to perform routing functions. Insome applications, the processor 1119 may perform signal duplication,addressing, signal deletion, signal insertion, signal monitoring,address adjustment, re-routing, request retransmission, update headerinformation, and/or insert or adjust control information.

FIG. 11C illustrates a CI transceiver adapted to decode received signalsintended for the transceiver and partially decode and route signalsintended for one or more other transceivers. System components shown inFIG. 11C are similar to components shown in FIG. 11B, as indicated bysimilar reference numbers.

The CI decoder 1103 applies one or more decode signals to the receivedbaseband signal. If the received baseband signal is coded with one ormore codes including complex conjugates of the one or more decodesignals, a sum of decoded baseband symbols over a code period combinescoherently. The combined symbols have a value associated with one ormore information signals. The combined symbols may be provided as a dataoutput after one or more optional signal-processing operations. Symbolsgenerated by the CI decoder 1103 are optionally processed in processor1119 prior to being coupled to a transmission system 1106 forre-transmission. CI-encoded signals not corresponding to complexconjugates of at least one of the decode signals (i.e., not intended forthe transceiver) contribute a substantially zero value to the combinedsymbols. The processor 1119 may be adapted to remove one or more signalcomponents intended for the transceiver. Since the signals intended forthe transceiver provide a dc offset to the individual symbols generatedby the CI decoder 1106, these signals may be removed by filtering,cancellation, or some other dc-removal process.

6. CI Routing and Control Methods

FIG. 11D illustrates a method whereby a transceiver in a network isprovided with control information 1151 that includes information used togenerate one or more array-processing weights 1153. Array processing1153 may be integrated into one or more transceiving functions 1153,such as transmitting, receiving, routing, and/or relay operations.

A subscriber unit (or any other network transceiver) may be adapted toprovide a directional or otherwise adaptable beam pattern. A beampattern may be considered to include any type of array processing,including, but not limited to, space-frequency processing, space-timeprocessing, spatial interferometry, null steering, diversity combining,spatial sweeping, and/or direction-of-arrival processing. A networktransceiver, such as a subscriber unit, may act as an antenna element inan array including other network transceivers. Thus, a networktransceiver may provide one or more weights to its transmitted and/orreceived signals as part of a larger array-processing scheme. Similarly,each antenna element of a multi-element network transceiver may beregarded as a transceiver element in a larger array. Each transceiverelement may be provided with weights as part of a largerarray-processing scheme. Array processing may be performed relative toone or more operational characteristics and/or objectives.

Array processing may depend on one or more network parameters, such asrelative location of each destination address, relative location of eachtransmission source, interference characteristics (e.g., origin ofinterference, time-domain characteristics, frequency-domaincharacteristics, polarization, power, etc.), channel characteristics(e.g., multipath, Doppler, etc.), link priority, link security, spectrummanagement, power control, and network loads. Array processing maydepend on the locations of one or more network transceivers, such asrelays, routers, access points, base stations, and other subscriberunits. Array processing may be adapted relative to changing locations ofother network transceivers, changing operational configurations,interference, frequency-reuse plans, channel conditions, power-controlspecifications, performance measurements (e.g., BER, probability oferror, SNR, SNIR, etc.), subscriber services, information type,modulation, formatting, channel selection, multiple-access protocol,frequency band, channel bandwidth, as well as any other Physical Layerand/or MAC Layer configurations.

FIG. 11E illustrates a method in which individual network transceiversare adapted to perform array processing relative to local conditions. Achannel-estimation step 1150 provides a characterization of thepropagation environment to better optimize array processing 1152 and/orCI processing. Any combination of sub-space processing (i.e., capacityenhancement) and diversity combining (i.e., signal-quality enhancement)may be performed. Array processing 1152 may be integrated into atransceiver-operations step 1153.

FIG. 11F illustrates an array-processing method that employs at leastone central processor to provide beam-forming operations across aplurality of spatially distributed network transceivers. Signalsreceived by the distributed network transceivers are coupled to thecentral processor, which performs channel estimation 1160 tocharacterize one or more communication channels. Various operationalcharacteristics and/or objectives (e.g., network parameters) areevaluated 1161. The evaluation 1161 can affect calculations ofarray-processing weights in a step 1162 that provides controlinformation to a plurality of network transceivers. Alternatively, thestep of providing control information 1162 may include applications ofarray-processing weights to signals received from and/or transmitted tothe network transceivers by the central processor.

FIG. 12A illustrates a method for providing CI-coded transmissions ofinformation and control signals. The method described in FIG. 12A may beperformed by a subscriber unit acting as a base station in a CI network.A CI code generation process 1201 provides CI codes and/or CI-basedcodes for at least one information signal and at least one controlsignal. A control signal may provide for one or more control functions,such as, but not limited to, power control, synchronization, codeassignments, priority assignments, link assignments, channelassignments, duplexing control, training-signal generation, notice oftransfer of control responsibilities, and request acknowledgement.Coding processes 1202 and 1203 encode the information signal(s) andcontrol signal(s), respectively. A transmission process 1204 providesfor transmission of the coded signals.

FIG. 12B illustrates a method for managing network control in a CInetwork by one or more subscriber units adapted to function as basestations. A CI transceiver acting as a base station transmits CI-codedinformation and control signals in a transmission step 1210. In anetwork identification and communication restriction step 1211, CI codescan be used, at least in part, to address the communication and controlchannels. CI codes can be allocated to restrict communications betweentransceivers permitted to operate in the network. CI codes can also beused to identify a radio network and each of the radio devices, as wellas the type of communications being transmitted.

A duplexing step 1212 provides for management of transmission andreception. Various types of duplexing may be employed, such astime-division duplexing, frequency-division duplexing, code-divisionduplexing, polarization-division duplexing, etc. A CI transceiver mayinclude a plurality of CI decoders in parallel to allow reception ofmore than one signal simultaneously. Similarly, transmission of codedsignals may be performed simultaneously with reception when thetransmitted CI codes differ from the code of the received signal.Furthermore, different CI codes may be used to encode transmissions todifferentiate types of transmitted signals.

A network-control step 1213 indicates that at least one of thesubscriber units becomes a network control station. A network controlstation initiates communications and maintains power control and timesynchronization of the network in the same manner that a base stationwould normally function. A transfer step provides for transfer ofnetwork control from at least one subscriber to at least one othersubscriber. The network control station can voluntarily transfer, or becommanded to transfer, power control and time synchronization of thenetwork to any other radio in the network.

FIG. 12C illustrates a network-control method of the present invention.A CI coding step 1221 provides different CI codes (such as may be usedto spread a signal) to information and control signals. A networkcontrol station may provide time-division duplexing 1222 to regulatetransmission and reception. A network-control step 1223 provides fornetwork control by the network control station. Network control 1223 caninclude various operations, including, but not limited to,synchronization, power control, code assignment, channel assignments,channel coding, transmission-path selection, load balancing, andspectrum management.

FIG. 12D shows a routing method of the present invention. A coding step1231 provides a multi-address, CI-coded signal for transmission in atransmission step 1232. The addresses may be provided by any combinationof CI coding and header addressing. Transmitted signals may be routedvia one or more paths through a network. A duplication step 1233 isprovided when transmission paths through a node diverge. Duplicatedsignals are transmitted along their respective paths.

In the methods and systems of the present invention, an address mayinclude any combination of coding and header information. A headertypically includes fields that provide control information,information-processing directives, waveform identification, networkidentification, and/or other information for enabling and facilitatingnetwork control and information processing. Tags are typically includedin a header of a transmission. An information signal may be providedwith one or more tags identifying the type of transmitted information,the amount of information, coding, number of addresses, routinginformation, and/or any other processing or payload information.

Header fields may include frame-sequence numbers, precedence, security,and end-of-message fields. A header may include a field indicatingwhether an acknowledgment is required from the destination node.Acknowledgments may be requested upon receipt, reading, and/or printingof received information. An extend field may identify whether an addressis an extended network address usable when the destination nodecorresponding to the network address has moved from one network toanother network. Information may be included in the header forforwarding a message to the other network. Information may be providedfor updating routing tables maintained at a node. An end-of-routingfield may be provided for indicating whether a network address is thelast address in a multi-address network header. Tags and/or addressinformation may be included in a preamble of a transmission.

FIG. 13A shows a relay method of the present invention. Received signalsare decoded in a decoding step 1301 at each node. The decoding step 1301may involve applying a code to a received signal corresponding to thecomplex conjugate of the node's address code. A processing step 1302processes information signals coded with the node's address code.Processing 1302 may include summing the decoded symbols and performinghard and/or soft decisions. Information signals addressed to the nodeprovide a de offset to the symbols of the decoded signal. This offsetmay optionally be removed 1303 prior to transmitting 1305 the resultingdecoded signals. FIG. 13B illustrates an alternative embodiment of arelay method of the invention. Some of the steps in the relay methodshown in FIG. 13B are similar to the steps shown in FIG. 13A, asindicated by similar reference numbers. A reverse-decoding step 1304provided between steps 1303 and 1305 applies the complex conjugate ofany codes applied to the received signals in the decoding step 1302.

FIG. 13C illustrates a transceiver processing and routing method of theinvention. A decoding step 1301 processes received signals with at leastone complex-conjugate code corresponding to at least one address codeassociated with the transceiver address and/or one or more predeterminedaddresses. Decoding 1301 may include one or more decoding processes,such as channel decoding, multiple-access decoding, spread-spectrumdecoding, and decryption. The decoding step 1301 may optionally includea level-detect function (not shown) to verify that a received signal ispresent prior to decoding.

A processing step 1302 is adapted to provide one or moresignal-processing steps to the decoded signals. The processing step 1302may estimate the values of information or control signals impressed ontoaddress codes corresponding to one or more complex-conjugate codesprovided in the decoding step 1301. For example, an adding step (notshown) may provide for coherent combining of addressed informationsymbols. A decision step (not shown) may follow the adding step (notshown). If any signal values are present, they may be passed to anoptional error detection/correction step 1311.

Error detection/correction 1311 may employ parity checks, trellisdemodulation, convolutional decoding, block decoding, and/or any otherchannel decoding or error-checking technique. Errors may be correctedvia receiver-side processing. Alternatively, error detection mayinitiate a request for re-transmission. Error detection/correction 1311may include re-quantization, channel estimation, channel compensation,predistortion of transmissions, multi-user detection, and/or optimalcombining. Error detection/correction 1311 may include decisionprocessing, including hard decisions and/or soft decisions. Decisionprocessing may include iterative feedback processing, such as turbodecoding.

The signal values may be provided to an optional system-function step1312. Confidence measures from soft-decision processes may be used toadapt receiver parameters (e.g., the processing step 1302), such as tooptimize reception. Similarly, received control information may be usedto adjust receiver parameters. System functions 1312 may include AGC,adapting filter parameters, adjusting quantization constellations,and/or changing sampling parameters. System functions may also includeremoving symbols or values associated with one or more predeterminedaddresses from the input signal values.

The signal values may be provided to an optional network-function step1313. Network functions 1313 may be selected or adapted relative toreceived control information. Network functions 1313 may includerouting, addressing, power control, synchronization, requestre-transmission, multiple-access control, channel selection,authentication, verification, identification, link-priority assignments,load balancing, spectrum management, and/or error processing. Networkfunctions 1313 may include adding, removing, and/or changing systemcontrol information.

Data and control information are re-encoded in a coding step 1304.Re-encoding 1304 may include the application of one or more codes,including address codes, multiple-access codes, spreading codes, channelcodes, and encryption. Coded signals are processed for transmission intoa communication channel in a transmission step 1305.

FIG. 13D illustrates a transceiver processing and routing method of theinvention. A received signal is duplicated in a duplication step 1300.At least one duplicated signal is coupled into a decoding step 1321 thatapplies a complex-conjugate code to the received signal. Thecomplex-conjugate code is related to the address code of thetransceiver. The decoded signal is processed in a processing step 1322to extract or otherwise estimate information values addressed to thetransceiver.

At least one of the duplicated signals is input to a secure procedure1310. For example, the at least one duplicated signal is passed througha fire wall (not shown). A decoding step 1316 provides for decodingsignals addressed to one or more destinations other than the currenttransceiver. A processing step 1318 is adapted to provide one or moresignal-processing steps to the decoded signals. The processing step 1318may estimate the values of information or control signals impressed ontoaddress codes corresponding to the complex-conjugate code(s) provided inthe decoding step 1310.

Processed signals may be coupled to one or more optional processingsteps, including error detection/correction 1311, system function 1312,and network function 1313 steps. The processed signals are encoded 1314prior to being transmitted 1305. Similarly, data input to thetransceiver is encoded 1324 prior to being transmitted 1305.

7. Scope of the Invention

In the preferred embodiments, several kinds of addressing, coding, androuting are demonstrated to provide a basic understanding ofapplications of CI processing in ad-hoc and peer-to-peer networks. Withrespect to this understanding, many aspects of this invention may vary.

For illustrative purposes, flowcharts and signal diagrams represent theoperation of the invention. It should be understood, however, that theuse of flowcharts and diagrams is for illustrative purposes only, and isnot limiting. For example, the invention is not limited to theoperational embodiments represented by the flowcharts. The invention isnot limited to specific network architectures shown in the drawings.Instead, alternative operational embodiments and network architectureswill be apparent to persons skilled in the relevant art(s) based on thediscussion contained herein. Also, the use of flowcharts and diagramsshould not be interpreted as limiting the invention to discrete ordigital operation.

In practice, as will be appreciated by persons skilled in the relevantart(s) based on the discussion herein, the invention can be achieved viadiscrete or continuous operation, or a combination thereof. Furthermore,the flow of control represented by the flowcharts is provided forillustrative purposes only. As will be appreciated by persons skilled inthe relevant art(s), other operational control flows are within thescope and spirit of the present invention.

Exemplary structural embodiments for implementing the methods of theinvention are also described. It should be understood that the inventionis not limited to the particular embodiments described herein. Alternateembodiments (equivalents, extensions, variations, deviations,combinations, etc.) of the methods and structural embodiments of theinvention and the related art will be apparent to persons skilled in therelevant arts based on the teachings contained herein. The invention isintended and adapted to include such alternate embodiments. Suchequivalents, extensions, variations, deviations, combinations, etc., arewithin the scope and spirit of the present invention.

Signal processing with respect to sinusoidal oscillating signals aredescribed herein. Those skilled in the art will recognize that othertypes of periodic oscillating signals that can be used, including, butnot limited to, sinusoids, square waves, triangle waves, wavelets,repetitive noise waveforms, pseudo-noise signals, and arbitrarywaveforms.

The foregoing discussion and the claims that follow describe thepreferred embodiments of the present invention. With respect to theclaims, it should be understood that changes can be made withoutdeparting from the essence of the invention. To the extent such changesembody the essence of the present invention, each naturally falls withinthe breadth of protection encompassed by this patent. This isparticularly true for the present invention because its basic conceptsand understandings are fundamental in nature and can be broadly applied.

1. An apparatus, comprising: a radio receiver configured to convertreceived radio signals to digital baseband signals; atime-domain-to-frequency-domain converter configured to convert thedigital baseband signals to a plurality of frequency-domain symbols; anda blind-adaptive decoder configured to decode the plurality offrequency-domain symbols to produce estimates of transmitted datasymbols.
 2. The apparatus of claim 1, wherein the blind-adaptive decoderperforms at least one of blind-adaptive decoding and partially blindadaptive decoding based on information about the transmitted datasymbols.
 3. The apparatus of claim 2, wherein the information includes amessage symbol constellation.
 4. The apparatus of claim 1, wherein theblind-adaptive decoder is configured to perform at least one ofconstant-modulus, multiple-modulus, and decision-direction processing.5. The apparatus of claim 1, wherein the blind-adaptive decoder isconfigured to perform at least one of dominant-mode prediction andcode-gated self-coherence restoral.
 6. The apparatus of claim 1, whereinthe blind-adaptive decoder comprises a combiner configured to combinethe plurality of frequency-domain symbols to produce the estimates ofthe transmitted data symbols.
 7. The apparatus of claim 6, wherein thecombiner is configured to perform at least one of orthogonalityrestoring combining, equal gain combining, minimum mean squared errorcombining, and maximum likelihood processing.
 8. The apparatus of claim1, further comprising an equalizer configured to operate on theplurality of frequency-domain symbols.
 9. A method, comprising:converting received radio signals to digital baseband signals;performing a time-domain-to-frequency-domain conversion of the digitalbaseband signals to generate a plurality of frequency-domain symbols;and performing blind-adaptive decoding of the plurality offrequency-domain symbols to produce estimates of transmitted datasymbols.
 10. The method of claim 9, wherein the blind-adaptive decodingcomprises a combination of blind-adaptive decoding and partially blindadaptive decoding based on information about the transmitted datasymbols.
 11. The method of claim 10, wherein the information includes amessage symbol constellation.
 12. The method of claim 9, wherein theblind-adaptive decoding comprises performing at least one ofconstant-modulus, multiple-modulus, and decision-direction processing.13. The method of claim 9, wherein the blind-adaptive decoding comprisesperforming at least one of dominant-mode prediction and code-gatedself-coherence restoral.
 14. The method of claim 9, wherein theblind-adaptive decoding comprises combining the plurality offrequency-domain symbols to produce the estimates of the transmitteddata symbols.
 15. The method of claim 14, wherein the combiningcomprises at least one of orthogonality restoring combining, equal gaincombining, minimum mean squared error combining, and maximum likelihoodprocessing.
 16. The method of claim 9, further comprising equalizing theplurality of frequency-domain symbols.
 17. A radio receiver comprisingat least one processor, memory in electronic communication with theprocessor, and instructions stored in the memory, the instructionsexecutable by the at least one processor to: perform atime-domain-to-frequency-domain conversion of digital baseband signalsgenerated from received radio signals in order to generate a pluralityof frequency-domain symbols; and perform blind-adaptive decoding of theplurality of frequency-domain symbols to produce estimates oftransmitted data symbols.
 18. The radio receiver of claim 17, whereinthe blind-adaptive decoding is based on information about thetransmitted data symbols.
 19. The radio receiver of claim 18, whereinthe information includes a message symbol constellation.
 20. The radioreceiver of claim 17, wherein the blind-adaptive decoding comprises atleast one of constant-modulus, multiple-modulus, and decision-directionprocessing.
 21. The radio receiver of claim 17, wherein theblind-adaptive decoding comprises at least one of dominant-modeprediction and code-gated self-coherence restoral.
 22. The radioreceiver of claim 17, wherein the blind-adaptive decoding comprisescombining the plurality of frequency-domain symbols to produce theestimates of the transmitted data symbols.
 23. The radio receiver ofclaim 22, wherein the combining comprises at least one of orthogonalityrestoring combining, equal gain combining, minimum mean squared errorcombining, and maximum likelihood processing.
 24. The radio receiver ofclaim 17, further comprising instructions stored in the memory andexecutable by the at least one processor to equalize the plurality offrequency-domain symbols.